Expand Eclipse variables in Initial Interpreter Commands

Adding the ability to expand variables to the initial commands allows
for some tighter integration between the Eclipse and the launched
python processes.
Merge branch 'development' into pullrequest/expand_eclipse_variables_in_initial_interpreter_commands
Merge branch 'pullrequest/expand_eclipse_variables_in_initial_interpreter_commands' of https://github.com/jonahkichwacoders/Pydev into jonahkichwacoders-pullrequest/expand_eclipse_variables_in_initial_interpreter_commands
Merged: initial interpreter commands can use eclipse string substitution (patch by Jonah).