Macros support.

Macro functionality is done through Annotations. When clicking on
expand macro annotation macro expands into the source code, annotation
to collapse is added to expanded region. When clicking on collapse
macro annotation macro is erased with expandee.

When triggering save command performSave function of
ScalaSourceFileEditor is called. Before actual save every macro is
erased with its expandee, so that source file doesn't contain any
macro applications.

Through createLineNumberRulerColumn function line number
column for custom line numbering is integrated. It internally stores regions, where
macros are and change line numbers where neccesary.

Macros can be turned off by clicking on the Enable macro icon,
M1+M2+M(Ctrl-Shift-M) shortcut or through preference page.
Simple rule: catch and log everything and don't risk to break users workflow with throwing when we don't know where it is going.

I think a thrown exception would be overwritten when the `super.performSave` throws, we need at least log it, this is what `safeRunner` is already doing. And we don't want to throw an exception here either, it is not safe to assume that it is catched. In a bad case we would break save functionality for Scala editors if this throws, in the worst we could bring Eclipse in an invalid state where it needs to be terminated by the OS (I already achieved that).