Parameter Sweeping for Benchmarking with R

moveit_benchmark_statistics.py
* Removed storing the planning request message in benchmark log files
* Added a new property of 'goal_name' for use with later results analysis
* Added an export to CSV function of benchmarking results for use with R, etc
* Added overwrite argument to easily reset the database file

benchmark_execution.cpp
* Added ability to do parameter sweeps
* Added more inline documentation
* Added new "workspace" and "workspace_frame" option to .cfg files for specifying the size of the planning workspace bounds
* Added new "sweep" option for specifying different methods of parameter sweeping during benchmarking
* Added new loop in benchmarking routine for changing parameters (sweeping)
* Modified the collected data to also work with different parameters, and to record them
* Created a modifyPlannerConfiguration() function