docs/installation: typo fix, clarification

 - Fix typo in rules path
 - Fix capitalisation.
 - `udevadm control --reload-rules` is unnecessary[1].
 - `adduser` is Debian-specific, use the more portable `gpasswd`.
 - No need to wait 10 seconds before re-inserting.
 - After adding to group, user must re-login.

 [1]: http://unix.stackexchange.com/a/39485/8250
added performance mx LED documentation

supplied by Alexander Hofbauer
doc/logitech: add HID++1.0 battery level info

This should help in https://github.com/pwr/Solaar/issues/49. This information
was shared by Nestor Lopez Casado from Logitech.

What remains unclear are the 0x25 and 0x26 values for r1 (Charging state). It is
also not clear whether r0 (Battery/Charging level) always reports 0x00 while
charging the Performance MX. (Perhaps this is only reported the first few
seconds?)
hid10: update 07 battery parsing based on spec

This fixes pwr/Solaar#49 partially, at least the charging state will be reported
correctly hereafter. The charge level may still be incorrect though.
Merge pull request #54 from Lekensteyn/doc-updates

Doc updates
Merge remote-tracking branch 'origin/master'
add favicon when building site
use passwd | addgroup in post-install
improved support for the Nano receiver
improved support for some Nano receivers
disable status polling on devices

the regular flow should be reading the battery on all devices now
don't support the VX Nano right now
updated scan-registers to support receiver scan
updated installation docs and udev rule install scrip
minor tweak to guessing device icon
show result on reg00 unparsable output
slightly reduce sleep timings when waiting for reply
solaar-cli: fix argument parsing in Python 3
solaar-cli: support specifying different receiver
Merge pull request #56 from Lekensteyn/cli-updates

solaar-cli: Python3 fix, add option for custom receiver path