Some parts of the README got obscured or dated with time. Let's improve them:
- Remove redundant text about keeping GIMP buildable (it's already said on
Cod. Style and Dev rights pages on gimp-web-devel, and not flatpak specific)
- Remove text about 1-hour timeout which isn't true according to my tests,
specially after the improvements of splitted jobs and updated build options
- Reorder Anitya text to before "module dropping" text, it's linear this way
("module dropping" by checking runtime is last step of module cycle of life)
- Remove very confusing "flatpak run... gimp" line which was breaking the
explanation flow about "module dropping" and it's not too useful since the
manifest (which is only a bit different) can be acessed in-source with tags
- Changed title from "Mantaining the manifest" to "Mantaining the modules"
- Added not so clear "Versioning the flatpak" to separate it from other modules
text. The title is not perfect, but at least make a needed pause on reading
AppImage is pretty fast to make, like the win crossbuild; and portable,
being very appropriate to do quick tests on Linux when pushing to git.
The overall organization of Debian jobs was changed to take advantage
of this and make things less complicated (but less clear at first sight).
I reinforce that this was the most efficent way to make the AppImage.
