support category=application|workflow process filtering

[fmigneault]

• add PROCESS_CATEGORIES full list in weaver.processes.contants (remove weaver.processes.types)
• rename corresponding variables to _CATEGORY instead of _TYPE to remove ambiguity between PROCESS_APPLICATION and PROCESS_WORKFLOW currently used for type field, and all below CWL_..._APP_TYPE
• set value into new category field of process (need to add migration of db)
• since Support a query parameter for matching the process type #642 would imply processType, maybe consider processCategory instead?