logview: always pickle the framed log data for faster reload

Fixes #1123

Pros:
* Much faster on subsequent loads of the same log file
* Pickle file stores the git hash

Cons:
* The pickle file is bigger than the original log file
* Total disk space is original + pickle
* Code in logview.py is a bit awkward with this hacked in

The log file from #1123 took 6mins to load the raw file and about 30-40s to load the pickled version.