add generation of unique abstraction name to extractions

Use the scope of the selected code to generate a unique name for the
extracted abstraction.

This moves the responsibility for avoiding name collisions due to
extractions from the IDE to scala-refactoring.
Fix build errors due to detected race conditions
Merge remote-tracking branch 'scala-ide/master' into feature-extractCode

Conflicts:
	org.scala-refactoring.library/src/test/scala/scala/tools/refactoring/tests/common/SelectionDependenciesTest.scala
	org.scala-refactoring.library/src/test/scala/scala/tools/refactoring/tests/common/SelectionPropertiesTest.scala
Merge pull request #51 from Luegg/feature-extractCode

add generation of unique abstraction name to extractions