This is basically skydb v2, except only for android.

I revisited some of the architecture decisions I made
in writing skydb.  I also separated skyserver.py from
dependency on skypy/paths.py since it wasn't really adding
any value.

We could make this way fancier, but this should at least
make working with SkyDemo.apk easier for now.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/960233007