Some check added to prevent errors on mepty file name upload. A very basic cache added to cache service object for a given url and user name. closes #11
New session used in callback code to prevent sqlalchemy thread error, localhost filecopy implemented. closes #12
session remote added to app.tear_down, check_same_thread=False added to connection string to ignore various related errors because new version of sqlite supports multithread access. ref #16
Cancelling support added. closes #17