docs: Get API docs working again

This changes around a few things that didn't work for me:
* Section names seem to be ostree-* instead of libostree-*
* Also XML files are ostree-* (they didn't show up at all)
- gtk-doc doesn't seem to parse const _OSTREE_PUBLIC correctly
* pull documentation is now on the actual functions rather than stubs
* Update gitignore with some more files

And there some changes to make gtk-doc give fewer warnings (not finished)

Closes: #327
Approved by: cgwalters

src/libostree/ostree-async-progress.c

@@ -23,7 +23,7 @@
 #include "ostree-async-progress.h"
 
 /**
- * SECTION:libostree-async-progress
+ * SECTION:ostree-async-progress
  * @title: Progress notification system for asynchronous operations
  * @short_description: Values representing progress
  *