This commit changes the way libraries headers are included in source files:
- If the header is in the same directory the source belongs to, so the
notation '#include ""' is used with the path relative to the directory
containing the source.
- If the header is outside the directory containing the source, then we use
the notation '#include <>' with the path relative to libraries folder.
Some of the advantages of such approach:
- Only one search path for libraries headers.
- OSs like Windows may have a better lookup time.
The compass.configured() method checks the eeprom and cannot be const
meaning the Arming object requires a non-const reference to the compass.
Removed check for null compass because the compass object is always
created although this could lead to unnecessary pre-arn check failures
even though compass-use is set to false.
