Make toggle_percenge field on Image reports 2.0 persistent per user.

Fix for bug 107.
https://bugs.linaro.org/show_bug.cgi?id=107

Change-Id: If79ba695996980fcc41a7d9b3ccf8d11960ceb2a
Image reports 2.0 docs update.

Add metadata docs, change image report chart filters adding/editing docs.

Change-Id: I59e0ef13edf076331ab2c87cf8d4e3c2e3b1cc00
Fix bug 118.

https://bugs.linaro.org/show_bug.cgi?id=118

Attaching bugs to image reports (both 1.0 and 2.0) is happening asynchronously now, hence no page reload is needed anymore.

Change-Id: I067db9b10f1b09b4a2402202978b5eaa9a925e33
PEP8 fix

Change-Id: I6aa1a86b03a931dce2eba05ca76657fb457bc160