Added upload of samples into existing project.

Added UploadSamplesMixin, and use it for HTML POST with /project/{projectid}/upload in ProjectUpload, and for API POST with /api/v1/project/{projectid} in ApiProject.

Got rid of obsolete upload.py file.
Sure, but the enumerate(reader) will be broken at soon as 10 errors are found. Since csv.reader is an iterator, the whole file is not yet read here, it's only read each time the iterator is called. 
So breaking the enumerate means breaking the reading. or am I completely mistaken ?