[LTK-Editor] Adapted content assist to use shared messages

Signed-off-by: Stephan Wahlbrink <sw@wahlbrink.eu>
[LTK-Editor] Cleaned up assist code

Signed-off-by: Stephan Wahlbrink <sw@wahlbrink.eu>
[LTK-Editor] Improved SourceUnitModelContainer
  - Made mode of accessible

Signed-off-by: Stephan Wahlbrink <sw@wahlbrink.eu>
[LTK-Model] Moved base implementation of FileBufferWorkingBuffer to core

Signed-off-by: Stephan Wahlbrink <sw@wahlbrink.eu>
[ECommons-Text] Moved classes for jface.text.rule to core

Signed-off-by: Stephan Wahlbrink <sw@wahlbrink.eu>
[Build] Added generation of source references

Signed-off-by: Stephan Wahlbrink <sw@wahlbrink.eu>
[LTK-Editor] Enhanced code folding
  - Added support for IProjectionPosition
  - Refactored to new package, nested classes to separate classes
[LTK-Editor] Improved handling for explicitly selected elements in editor
  - Added direct range hightlighting
  - Added support for to expand collapsed content regions

Signed-off-by: Stephan Wahlbrink <sw@wahlbrink.eu>
Fixed code style

Signed-off-by: Stephan Wahlbrink <sw@wahlbrink.eu>
[LTK-Editor] Fixed CCE for non-workspace files

(reported by Tobias Verbeke)

Signed-off-by: Stephan Wahlbrink <sw@wahlbrink.eu>
[LTK-Editor] Added workaround for E bug #438919: CCE/ContributionInfo in
outline view

Signed-off-by: Stephan Wahlbrink <sw@wahlbrink.eu>