sql.py: pkey(): Use pkeys cache from db object instead of parameter

sql.py: Wrapped db connection inside an object that can also store the cache of the pkeys and index_cols

bin/map: If cpus is 0, run without Parallel Python

bin/map: Set up Parallel Python with an env-var-customizable # CPUs

bin/map: Set up Parallel Python with an env-var-customizable # CPUs

root Makefile: python-Linux: Added `sudo pip install pp`

root Makefile: python-Linux: Added python-parallel to installs

mappings: Build VegX-VegBIEN.organisms.csv from VegX-VegBIEN.stems.csv instead of vice versa. This entails switching the roots around so stem points to organism instead of the other way around, which is a complex operation. Re-rooted VegX-VegBIEN.organisms.csv at /plantobservation instead of /taxonoccurrence to avoid traveling up the hierarchy to taxonoccurrence and back down again to plantobservation, etc. as would otherwise have been the case.

bin/map: When determining if outer elements are types, look for /*s/ anywhere in the string instead of just at the beginning, because there might be root attrs (namespaces), etc. before it

bin/map: When determining if outer elements are types, look for /*s/ anywhere in the string instead of just at the beginning, because there might be root attrs (namespaces), etc. before it