build: Replace 'waf clean' by removing build dir.

The 'waf clean' doesn't work reliable in some situations.

Merge origin/master into master

bootloader: Add binary for 0.5.0.

libbsd: Pull in bug fix.

bootloader: Slim down.

Beta version of toolchain for GRiSP base Ver.: 1.2

grisp-bootloader: Remove old README.

grisp-bootloader: Change config format.

This closes #11.

bootloader & libbsd: Disable USB and WiFi for GRiSP bootloader.

bootloader: Add binary for grisp V1.1.