The build process fixup PR to rule them all

Alright, sorry about all the noise with pull requests. I figured breaking up all of my changes to the build process would make it easier to merge, but really it just made it harder to get reviews. So here I am with a single pull request with changes to the build process for:
  * speech synthesis
  * MAVLink dialect selection
  * libxbee
  * QUpgrade

Note that this pull request includes and expands upon the changes in #483, #485, $586, and #488. Also includes additional change of updating the README's repository layout section.