Make the Presentation Compiler start after quiescence

Creates a ScalaReconcilingStrategy that follows the IReconcilerExtension route to using an [Eclipse Reconciler](http://wiki.eclipse.org/FAQ_How_do_I_use_a_model_reconciler%3F).
This Strategy defers the Error Annotation update it triggers to a ScalaEditor.


Monkey-tested : markOccurrences, code completion, quick Fixes, Hyperlinking, Errors As You Type
Expected not to work (until rebase on [PR 309](https://github.com/scala-ide/scala-ide/pull/309) ) : Semantic highlighting

Testing : more integration testing, based on re-implementation of features from org.eclipse.jface.text.tests, to come soon