Make BooleanValidator accept bytes too besides int

Previously, only the first parameter byte can be read or written. After this
patch, it is possible to select/write more bytes by specifying a mask of type
bytes with the appropriate length.
Support FN keys swap for K800
Add K710 with FN key swap support (pwr/Solaar#18)

The K710 keyboard is (according to the issue reporter) part of a MK710 combo
(which also contains a M705 mouse). Observing a succesful 07 register read,
I think that it is a HID++ 1.0 device too that uses the same register for FN
key swapping as K800.
Fix battery status reading, add "fully charged"

Commit 438c501fae2486f1520eb485c14662c3a632fd2c introduced support for HID++ 1.0
battery information. That accidentally selected the third parameter instead of
the second one. This commit fixes that and additionally adds a "fully charged"
status too that was found on the K800.
Merge pull request #26 from Lekensteyn/hid10-battery

Fix battery status reading, add "fully charged"
Merge pull request #24 from Lekensteyn/hid10-fnkey

Add FN key swap support for K800 (and presumably K710)