Change data store to rappdirs directory

Conflicts:
	DESCRIPTION (two new packages imported)
load_fcdata returns object when rds contents loaded

* closes #29
* also warns when loading rda objects containg >1 object
  or when object and file name don't match
Merge branch 'feature/rappdirs'

* feature/rappdirs:
  Change data store to rappdirs directory

Conflicts:
	DESCRIPTION (packages added in each branch)