ISIS-463: can now intermix @unit and @integration level specs.

* renamed ScenarioExecution's get and put to getVar and putVar
* added a removeVar
* updated corresponding convenience methods in IntegationTestAbstract and CukeStepDefsAbstract
* added supportsMocks into CukeStepDefsAbstract
* refactored todo specs with guards (necessary, unfortunately)
- InMemoryDB utility class refactorings
- fixed license header comments.