Add turnTo method to inertialNav

When inertial nav is enabled the turtle can be instructued to turn
towards a certain direction.
added goTo and goToStart methods to inertial nav

- Add goTo and goToStart methods to the inertial navigation API
- Change turn directions to go right for positive numbers instead of
left.
-Enhance the digPit method to make it return to the surface
automatically when it's inventory is full.
Optimized digPit

It now digs down 2 rows at once ! (it mines the block in fron of it as
it goes down). Since this is a hack job atm it doesn't support odd
lengths.
Added an "error_on_failed_move" option to terrapin
Renamed clearMountain to clear
Cleaned up digTunnel

- Changed parameter  order. height is now last.
- Whistespace fixes
- Removed debug output
misc changes
Cleanup the directory structure

Moved all the actual terrapin release files into a subdir : terrapin/
Add the terrapin_web turtle server
Fix checkins

checkin.pushTask must be called before we can start sending updates
Extend checkin data

By default the relative position willbe sent (if inertial navigation is
enabled) and the current taks is now correctly retrieved.
Reset the cursor position after clearing the screen-