Introduction of STRING datatype.

* FE-Keyboard update, new String button.
* values.../strings.xml update
* Implementation of Dialog to create strings.
* Adaptation of Internformula classes.
* Interntoken update.
Raw implementation of string functions.

* length of some 'string' function
* lettter x of some 'string' function
* Lint warning fixes.
* String highlighting after user selection.
* Empty String as parameter possible.
* Compute Dialog Refactoring.
* Display of Character returning functions in ComputeDialog.
join() begin of implementation

* Abstract interpretation of function parameters.
Extended implementation for join()
* Test adaption.
* Test and Bugfixes.
* Equal operator for strings.
* Extended test for letter() + bugfix
UserVariable holds an Object now instead of a double.
* Stringfunctions can use UserVariables as parameter.
* The 3 stringfunctions (length(), letter(), join()) can now handle
  parameters of the type UserVariable.
* Implementation of tests.
SetVariable- and ChangeVariableActionTest refactoring and extension.
* ChangeBrightnessByNAction - SetSizeToActionText extension.
* Stringformula interpretation for Change...-Bricks.
* Stringformula interpretation implementation and extension of test:

* GlideToAction
* GoNStepsBackAction
* IfLogicAction
* Lego...Action (no tests)
* MoveNStepsAction
* PlaceAtBrick (only tests)
* RepeatAction
* PointInDirectionActionTest

Stringformula interpretation in BrickAction:

* TurnLeftAction
* TurnRightAction
* WaitAction
* All Set...-Actions
Initial string tests for operators and functions.
Refactoring of Stringparser tests:

* Introducing new FE-Util class.
* Introducing ParserTestOperators class.
* Moving methods to responsible class.
* Rewriting pompous code.

Stringparameter tests for normal functions.

Stringtests for addition, subtraction, division and multiplication.

* Refactoring (Rename of testclasses)
* Testmethod of SensorLoudnessTest moved to SensorTest

General Refactoring of code:

* License Header added.
* Extension of the FormulaEditorUitl Class.
* Removing spam code.
Not a number (NaN) handling in every brick action:

* Formula interpretation to NaN will be handled + test.
* Null-Formula tests.
* Stringfunctionhandling of Not-A-Number parameters.
Note- and SpeakBrick now use FormulaEditor.
Substraction a NUMBER from a Stringfunction caused and uncaught exception.
Prototypeview for Mathfunctions.
Delete of unused resources in strings.xml

Note- and SpeakBrick test update:

* testSoundBrickDefaultValues update
* testComputeDialog update

Fix of lint and checkstyle warnings.
Fix of Checkstyle, PMD and FindBugs warnings.

Update of Formula Editor Keyboard:

* Remove of RAND-button and update of tests.
* Update of STRING-button width.
* Math changed Functions on english keyboard.

Fix of FindBugs warnings.
Concrete exception catching in actions.

* ChangeVariableAction and IfLogicAction return true in act() method
  Formula can not be interpreted.

Refactoring of Formula interpretation methods.
Refactoring of BrickViews with Formula.
Refactoring of Actiontests with Formula.
Fix of 2 failing tests.
Language version upgrade.
Note- and SpeakBrick use new Formula mechanics.

IfLogicAction- and RepeatActionTest: testNullFormula() update.
Fix of some Brickrefactoring related UI-tests.
CatrobatLanguageVersion support. (Note- and SpeakBrick language conversion to FormulaBrick)
Remove of redudant Null-Formula test method (SpeakStageTest.testNullText())
fix for Note and Speak Brick
SpeakAction sprite parameter setter.
Merge pull request #970 from Catrobat/DatatypeString

Formula Editor: Strings
merged userbricks with current master
fixed GSOCSF-6 Variabletext doesn't get deleted
fixed GSOCSF-7 (NullPointer Exception in AddBrickFragment - OnDestroy()
fixed GSOCSF-8 Backstack of Script does not get updated correctly after deleting a userbrick
fixed GSOCSF-9 Define brick should not be deletable/copyable
added "testDeleteUserBrickAndCheckIfScriptActivityUpdates"
fixed GSOCSF-10 1 Userbrick variable is accessible in Script when using more than 1 Userbrick
fixed GSOCSF-12 Dropdown menu of change variable and set variable have partly UserBricks scope
added "testMoveUserBrickUpAndDown"
added "testCopyAndDeleteUserBrickFromScriptWithBothVariants"
fixed GSOCSF-13 Define brick can still be selected in copy/delete ActionMode
fixed GSOCSF-14 When copying any brick in UserScript via ActionMode it gets copied to Script
added "testEditFormulaWithUserBrickDataAndChangeValuesViaFormulaEditor"
added "testChangeDeleteUserBrickData"
added "testUseUserBrickVariableInFormulaAndDeleteVariableInFormulaEditor"
added "testCopyAndDeleteBricksInUserScriptInclDefineBrick"
fixed GSOCSF-2 Don't allow recursive UserBricks
fixed jenkins errors:
 - added assertions to all tests
 - added german translations (dummy) for missing strings
 - replaced the license from master to two files where jenkins said it was missing/not correct
 - a few spaces where not copied correctly
fixed jenkins lint&checkstyle errors
fixed jenkins lint&PMD errors
fixed LAST jenkins lint&PMD errors
alertDialog was not closed properly
in testCreateNewBrickButton one click was wrong
changed 2 tests of mine to work properly on jenkins
changed onDestroy() of ScriptActivity
changed dragFloatBrick parameter to -1
added scrollUp(), test still fails on jenkins for no reason
removed test, because redundant
adding userbrick to userbricks is now disabled!
changed german string value of Toast when adding userbrick to userbrick
don't show toast now, add a Userbrick to an existing Userbrick is just not possible anymore for now
When deleting Userbricks in "AddBrickFragment" the Actionmode Title is updated correctly
fixed GSOCSF-19 Using parameters in a userbrick doesn't work in some cases
fixed GSOCSF-17 Forever loop gets inserted in wrong way
changed SpriteTest and removed unused imports
don't show toast now, add a Userbrick to an existing Userbrick is just not possible anymore for now
When deleting Userbricks in "AddBrickFragment" the Actionmode Title is updated correctly
GSOCSF-20 deleted testNullSprite and tried changes in PreStageActivity, problem didn't return.
rebase to refactored bricks
rebase to strings