Merge pull request #8 from ericdill/devel

MNT: Documented search and added type checking to input parameters
Removed mongoengine: Change database tables and raw commands to make code dependent only on pymongo. Tested using the sample code for all supported apis
Added unit test for databaseTable.Header
Moved sample code for various apis into metadataStore.example. Added debian server start script to metadataStore.demo
MNT: Added checking for scan_id being None to commands.py
MNT: Raise a ValueError on bad search keys, don't log it silently
Fixed no event return in search(.., data=True)
ENH: Added type checking and input validation to userapi.commands.search
Merge remote-tracking branch 'dill/devel_dill' into devel