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.
This is a complete rewrite of the GPS driver structure, with a static
main driver and separate backend drivers. This will allow proper
support for multiple GPSes, and will allow parameters to be set on the
GPS object