Adds support for Scala 2.12
Bumps to master sbt version
Adds 2.12 support in ScalaInstallationTests
Adds 2.12 support to ClasspathTests
Adds support for 2.12 in breakpoint tests
Specialize Scala 2.11 feature for 2.11 and 2.12 build

The Scala 2.11 feature for the 2.11 build has a reference to the bundled
Scala 2.10 jar. We don't want this reference for the Scala 2.12 build.

This will be removed when the need of the bundled Scala 2.10 jar is fixed.
Fixes shortString method for version <= 2.9

And move common code in CompilerUtils
Merge pull request #727 from skyluc/2.12-support

Adds support for Scala 2.12
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.