Stabilizer: Added acceleration vector magnitude log variable

Can be used for stuff like free-fall detection. Value sent is the square of the
magnitude (sqrt is cheaper on the pc side).
sensorfusion6: Fixed roll/pitch/yaw calculation

Follows equation found on http://www.chrobotics.com/library/understanding-quaternions
sensorfusion6: Fixed euler angle calculation asin() crash

Clamping gx in [-1, 1] to prevent asin() from crashing the copter
Added tag 2014.01-rc1 for changeset f826511b6a16
log: create_block returns EEXIST if a log block already exists
Added tag 2014.01.0 for changeset 54fa51cb6ea0
Merged fixes from 2014.01
Fixed I2C2 initialization
Make the version-scripts git-aware

Some people prefer to use git (easy possible by using git-hg) therefor
make the version-scripts git-aware.

To not change the view of the version string(s), the version when using
git still looks the same as if mercury is used (and not like a
standard git-version).
Fixed make cload by updating references to crazyflie-clients-python
Merge branch 'master' into gps_ublox_dev
Early implementation of uBlox binary GPS decoding and logging