Split the AppStream parsing and writing into two phases

This allows us to merge the font files that are in seporate subpackage names.
Do not validate font AppData files
trivial: More formatting fixes to the font parser
Add the font AppData metadata entries
Revert "Prefix the IBus input methods with 'ibus-'"

This reverts commit b08cd7ddaa67cb16c6359c098f6ec3942f0853d9.