Some Kidle refresh mode experiments...

Emulate (as best we can) the refresh behavior of the Kindle Touch reader
Try to use reagl on the PW2...

That doesn't seem to work as nicely as the stock reader... :/
Clear up some comments...
Another hugely important commit!
One more comment...
Keystrokes aren't that cheap.
Update koreader-base.

For the backend changes related to #704
Fix the battery checks.

I have *no* idea how that even seemed to work, but in fact didn't.
Also no idea where the hell is the battery status supposed to appear in
the menu, because it's currently not there.
Add a battery indicator to the menu.

Very quick'n dirty hack, doesn't seem to blow up horribly.
re: #679
Merge pull request #704 from NiLuJe/master

Some Kindle screen refresh experiments (bis)...
Detect the EU 4GB WiFi PW2
Add a warning about the waveform mode constants...

Note that they're from the Kindle driver, the Kobo one might expect
slightly different values...
Move the waveform mode selection a bit...

Move it from the main UI loop to init, we're using static values anyways,
and a change of device at runtime is highly unlikely (:D).
Add the Noto font family to our ressources.

It's basically Droid, but maintained.
Will tweak the defaults later.
Use Noto instead of Droid, where appropriate.
Add an installer/updater to the KUAL ext.

And also play with some CRe settings, for kicks.
Meh...

It's not even funny when everything works straightaway...
Add kerning tweaking to the KUAl ext
Make the CRe KUAL buttons conditional
Ha, of course, I forgot the dubest thing ;).

Cleanup behind us after an update/install ^^.