Generate API docs from source code comments (#2491)

* Generate api docs from source code

* Add a bunch of doxygen comments

* more doxygen comments

* Add the in-progress api docs

* script to generate docs from travis

* Add doc generation to the travis job

* make travis_docs.sh commit the work it does

* make sure the docs script exits cleanly

.gitignore

@@ -23,6 +23,7 @@ quantum/version.h
 .idea/
 CMakeLists.txt
 cmake-build-debug
+doxygen/
 .DS_STORE
 /util/wsl_downloaded
 /util/win_downloaded
@@ -65,4 +66,4 @@ util/Win_Check_Output.txt
 # things travis sees
 secrets.tar
 id_rsa_*
-/.vs
+/.vs