test: each app keeps its tests in a tests package

131 test modules sat next to the code they test; instances alone had
51 of them beside views.py and utils.py. They move into a
tests/ package per app, and the JavaScript checks into
webvirtcloud/tests/js. Each non-empty tests.py becomes tests/test_views.py;
the empty generated stubs are removed.

Imports of the app's own modules become absolute, paths built from
__file__ go one level up, the live helper is instances.tests.livetest,
and coverage omits */tests/*. The suite discovers the same 960 tests as
before.

datasource/tests.py

@@ -1,2 +0,0 @@
-
-# Create your tests here.