Provisionally added error source and header file. This is provisional because it should be replaced with the err.h and err.c file in the PX4 stack but first some issues have to be solved
Added empty source file for perf_counter.h from the PX4 stack. The functionality should be added later, for now it is ok if it's just empty
Source files for controller lib is now included from the PX4 repo (src/lib/ecl/attitude_fw/)
Changed include definitions, since many headers are now directly included from the PX4 stack (mathlib, ecl, ...)