Django 1.11 is supported, but seafile-admin was still looking for v. 1.8.
Replaced current patch with the patch from haiwen/seafile-server#147.

Cleaned up unsupported configure options, including riak backend.

Check that the seafile-server version is the same as seafile-seanet's at
build time, removing the static EXTRA_DEPENDS check done at install
time.

Signed-off-by: Eneas U de Queiroz <cote2004-github@yahoo.com>

Switched to codeload for simplicity and easier package bumping.

Signed-off-by: Rosen Penev <rosenp@gmail.com>