Remove unused field.
Refactor scala version comparisons, better handling of unkown versions
Extends compatible versioning to cover for the XSource case.

Changes Error to suggest use of the XSource flag.
Reuses ScalaVersion from the compiler.

De-Optionalizes, De Stringifies version comparisons
Relegates Xsource setting computation to projects

THis prohibits from having a workspace-wide Xsource setting, for now.
Treats absence of XSource configuration as exception
Remove cruft, hardens version spec in prefstore
corrects the case where the user adds the XSource flag on a modern code base

Fixed error message
Cleaner error messages on version checks.
Hardens classpath test sequence
Uses the rigth preference store

Conflicts:
	org.scala-ide.sdt.core.tests/src/org/scalaide/core/classpath/ClasspathTests.scala
Merge pull request #669 from huitseeker/issue/Xsource

Xsource internal support & ScalaVersion upheaval
Removes pendingSources, which shadows sources

Fixes #1002070
Merge pull request #671 from huitseeker/pr/668

Simplifies EclipseSbtBuildManager
Remove CollectionUtil
Remove file withDocument and move its content to EditorUtils
Merge RichAnnotationModel into AnnotationUtils

The only functional change is that JavaConversions is replaced
by the more explicit JavaConverters.
Remove Editor, EditorUI and RegionHelper

Those files were unused
Refactorings in EditorUtils class

- Non UI logic of `applyChangesToFileWhileKeepingSelection` is moved to
  its own method
- The class EditorHelper is removed because its content overlaps with
  EditorUtils (and it was unused anyway)
- The package ui.editor.util is removed
Merge pull request #677 from sschaef/t-cleanup-codebase

cleanup codebase