Some people read the "Getting Started" section as a series of
incremental lessons, and having the examples go from GtkApplication to
the old style "init / spin the main loop" confuses them.
We should be using GtkApplication everywhere in our examples.
As part of the conversion, give up on including
sources files from the examples directory, and
instead include the content directly. All include
mechanisms add complications. They were already
complicated with xml, and markdown is not making
things easier.
We already did that for fragments, and if you
make changes to these example sources, you
probably need to revise the surrounding text
anyway.
