Initial commit of ProcessTree plugin and test

ProcessTree uses recursive database queries to traverse the
process_input_well and process_output_well tree keeping track of
paths (aka trails).

Also provides fast access to design well information from plates fo
wells further down in teh hierarchy.
Modified ProcessTree tests
Completed initial tests for path retrieval and started testing for plate design retrieval
Further test development for ancestors of wells
Merge branch 'devel' of github.com:htgt/LIMS2-WebApp into process_tree
Commented out tests under development
Merge branch 'devel' of github.com:htgt/LIMS2-WebApp into andrew_summaries
Modified summaries well descend to use new version of ProcessTree