Trying to get better class calls working.
Enforce PressForward singleton in pressforward() bootstrapping function

This ensures that the PressForward singleton can't be loaded more than once.

See #217
Don't set up PF_Feed_Item properties until pressforward_init

This prevents infinite regress errors when PF is loading. See #217
Trim trailing whitespace
Replace calls to $pf global with pressforward() singleton function

See #217
Merge pull request #218 from PressForward/3.0.x-better-class-calls

3.0.x merge better class calls with 3.0 improvements.