Move the exit condition into a special function

The program will now stop, if the user type 'exit' or 'quit' into the console
Move some global variables to the utils module
Add general section processing
and code cleanup
Add parse_to_bool function

add global variables (which were moved out of the brickltes module)
Move global variables into DataLogger class
Add xively variable

This variable indicates if we'll log to xively or not
Refactored due to changes in the bricklet constructor
Merge branch 'master' of https://github.com/D4wN/brickv

Conflicts:
	src/brickv/data_logger/bricklets.py