Change input file's behavior of loading families in database through `kineticFamilies` field.

Prior to this, if kinetics library was listed as 'default', or 'all' this does not get
carried through- rmg.kineticFamilies gets set to None in both cases.

Behavior now:

If `kineticsFamilies` is set to 'default' or completely omitted from input file,
this is interpreted as 'default' setting when loading families.  Currently this means
we load all families.

If `kineticsFamilies` is set to 'all', all families are loaded.

NEW: If `kineticsFamilies` is set to 'none', none of the families are loaded.  (Good for
debugging purposes).

If `kineticsFamilies` is a list:
	If list is empty: all families are loaded
	If list contains families marked with !, those families are not loaded.  ie.
	!R_Recombination loads everything but that family
	If list contains a few families, then it loads just those families.

Added additional error raising in rmgpy.data.kinetics in case any of the if/elif
statements fall through when code changes occur.