Basic datastore functionality with history items

Database is stored in documents directory
Separated database access into a singleton utility class

Also updated home view unwind method to empty
history items from array so the same item doesn't
get added multiple times from the database
Calibration value popup shows a more appropriate keyboard
Results view unwind

Hitting the done button on the results view now unwinds to the
appropriate source view controller (test or home)
Support for subject/notes fields