Add notes field to result model

Also add transforms to set the notes field for Maryland
precinct-level results and update Maryland validators to
check sub-racewide totals against election day totals instead of
total totals.

Addresses https://github.com/openelections/core/issues/130,
https://github.com/openelections/core/issues/123
Update logic for registering transform functions
Update bulk transform syntax

Addresses https://github.com/openelections/core/issues/130