Reduce code duplication in the different api endpoint
pep8 fixes
Add the anonymous upload api endpoint
Add boolean field `authenticated` in the kerneltest table

This field stores whether the user was authenticated when he/she submitted
his/her results.
Specify for each upload endpoint whether the user was authenticated and store this in the database
When the user uploads his/her results via the web UI, directly use his/her FAS username

So there is no need to ask for an username in the input page.
One cannot use the anonymous upload endpoint to pretend to be kerneltest