Move `TestsSuite` to `org.scalaide` package
Add `FileCreator` interface

This interafce is public API
Add `ProjectUtils` and `Commons`

These class contain helper methods used by the new file wizard.
Start implementing `ScalaFileCreator`
Add validation logic to `ScalaFileCreator`

There is one flaw left in this validation logic: It only checks if an
identifier is a valid Java identifier and if it is no Scala keyword. For
package paths it should also check if they are no Java identifiers and
for file names it should check if the name is a valid Scala identifier
(which can contain special signs).
Add logic to `ScalaFileCreator` that generates template variables
Enable wizard tests in test suite
Add file creation logic to `ScalaFileCreator`

This doesn't contain any tests because tests that check changes to the
file system are difficult to write.
Add org.scalaide.ui.wizards.fileCreator extension point
Add new "New File Wizard"

For more information about this wizard see the proposal that can be
found in the associated ticket.

Fixes #1002103
Add combo box that can show images

This introduces a dependency to the Eclipse Nebula project because a
combo box that can show images is not part of SWT or JFace.
Validating logic now checks Scala and Java keywords

Previously it was only checked if identifiers can not correspond with
Java identifiers which is not enough for Scala identifiers.

Furthermore package names are not allowed to contain Java identifiers.
The Eclipse package hierarchy view can't display them correctly and even
the Java compiler of JDT seems to have problems with them.
Create first file creator for the new file wizard
Add file creator for traits
Add file creator for objects
Add file creator for package objects
Show error messages for package objects on wizard creation

The default behavior was that no error messages are shown at wizard
creation. For package objects this behavior is not the most useful one
because it can be that the initial path is already valid. In case it is
not users show be notified about this immediately.
Add file creator for apps (classes that extends the trait App)
Add selection listener to combo box in new file wizard

Without the selection listener there does no validation of the file name
happen when users change the type of the new file with the mouse instead
of the keyboard.
New file wizard doesn't create linked mode anymore

The linked mode turned out not to be very useful. The only thing users
really want is that the cursor is placed at the correct position after
the file is created, which is still supported. All other markers that
belonged to the linked mode were removed.