libpixi: move APP_ log macros into libpixi/util/log.h
libpixi: fix command.h source doc
Fix pre-build dependency ordering
Fix some install dependencies
Add missing uninstall code
Build pixi-ext by default, but don't install it
Move extensions/ to examples/ and install those examples

Also install the README.
Install python files last, to get the right python2.7-files
Add uninstall of API docs
Set the default FPGA file to /etc/pixi-tools/pixi.bin

It's up to the user to make a symlink at /etc/pixi-tools/pixi.bin
pointing to the default file.
pio: log.h requires util/app-log.h
pixi-tools-0.5