Implementation of conditional breakpoints

Based on expression evaluator.
User interface for expression evaluator

Complete with history command, tree view for values, simple content
proposal and multiple configuration parameters.
RunSelectionInInterpreter action added

Runs currently selected text in expression evaluator view.
AUTHORS file updated with names of expression evaluator authors
Ignoring tests for conditional breakpoints

Those tests hangs on Scala IDE Jenkins, but we could not reproduce those
hangs neither on Linux nor on Windows so we could not fix it.