First entry in CONTRIBUTING.md

Notes about making database changes
Add patches directory
modifying the database to add a status on the raw data
Fixing tests due to changes in db
Adding add_filepaths_status property to RawData
Adding util functions to manage filepaths
Adding the clear_filepaths and remove_filepath function to the RawData object, and their tests
Removing unused variable
Addressing comment
Solving merge conflicts and fixing test failure
Adding failed status to the add_filepath_status
Adding ability to remove all filepaths from a RawData form the GUI
Missing bits for removing GUI
Adding add_raw_data functionality to the study
single raw_data -> list of rawd ata
Adding existing raw data to study connection
Fix merge conflicts
Fixing bug on test that only shows up on Travis
adding investigation type to PrepTemplate.create and the investigation setter
Refactoring of the purge filepaths function