put ontology file extensions to database
rename seed files for more space in between
add functions for retrieving extensions from db
fix failing tests by stubbing ontology extensions
move file extension saving into migration
remove unneeded seed file
use ClassMethods instead of included
use pluck_select
use proper class method call
remove id from file extensions db table
add missing inclusion
Merge pull request #834 from ontohub/330-file_extensions_in_database

330 file extensions in database