Allowing the test plan to be initialized with params and Adding the bsh_post method to the DSL

\We added the possibility to initialize the test plans with params. We had to do this, since we have to create a test plan with two thread groups that had to run sequentially. Therefore we have to pass in the 'serialize_threadgroups=true' param to the test_plan constructor. The test method didn't allow that, so we added that capability.

Also, we added the short cut for the beanshell postprocessor.

In the first commit, we add the Rubymine config files (in the .idea folder) to gitignore