Safer default MOT config for M4 with onboard ESCs;
Allow build with custom config defaults and board definition files;
Allow M4 build for external ESCs only (-DUSE_EXTERNAL_ESC);
Makefile add CONFIG_FILE and BOARD_FILE variables for custom builds.

git-svn-id: http://autoquad.googlecode.com/svn/trunk@434 69e9ae41-46e5-6d7e-5b29-2a8ba9409dbb
Fix missing makefile update.

git-svn-id: http://autoquad.googlecode.com/svn/trunk@435 69e9ae41-46e5-6d7e-5b29-2a8ba9409dbb
Add forgotten config_defaults_m4 :(

git-svn-id: http://autoquad.googlecode.com/svn/trunk@436 69e9ae41-46e5-6d7e-5b29-2a8ba9409dbb