The PSTR is already define as a NOP for all supported platforms. It's
only needed for AVR so here we remove all the uses throughout the
codebase.
This was automated with a simple python script so it also converts
places which spans to multiple lines, removing the matching parentheses.
AVR-specific places were not changed.
- abstracted verify_command so that command-wide actions can happen more cleanly, namely mission_item_reached
- This also brings the structure in line with plane and rover
