Implemented support for 1.5 libraries specification rev.2

- removed "arch" folder support
- allow to optinally use "src" folder
- slightly changed metadata

For more information see:
https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5:-Library-specification
http://goo.gl/gfFJzU
Added a warning for library using the no longer supported "arch" folder
Use Files instead of String to handle paths in Compiler class.
IDE do not hide libraries with incompatible architectures
Added "category" field in libraries.
Added "license" field in libraries.
IDE warns if a library is compiled with an unsupported architecture
Added the possibility to override library compatibility check
Removed unused import
GSM library to format 1.5 rev.2
Audio library to format 1.5 rev.2
Robot Control library to format 1.5 rev.2
Servo library to format 1.5 rev.2
Merge branch 'lib-1.5-rev2' into HEAD