Refactoring in indentation suite

- Activate the indentation test. For this to happen larger
  refactorings were necessary. All the UI dependencies
  had to be split out of the indentation logic in order to
  avoid a triggering of the UI classes. For this a lot of
  code of the internals of JDT is directly copied to SDT.
- Rename TestScalaIndenter to ScalaAutoIndentStrategyTest
- Replace existing test evaluation with the newer one from
  AutoEditStrategyTests
Start implementation of first indentation test classes

It turned out that it is not easily possible to test all possible
sort of indentations. Indentation triggered by tabs for example
are handled by a different component and it is not easily possible
to disable this behavior and merge the different parts that are
responsible for indentation.
Implementation of first class indentation tests
Simplify TestCommand in AutoEditStrategyTests
Replace PreferenceProvider with PreferenceStore in indent suite

TODO:

- Remove class PreferenceProvider
- Remove class JDTPreferenceProvider