Application Development chapter refactor

See merge request Librem5/developer.puri.sm!102

Move the Design section into the App Development Guides.
Add placeholder guides.
Tidy up the GNOME documentation.

Add a Guides section.
Move the Flatpak setup information up a level.

Prepare to move parts to sections on packaging and publishing.

Devkit handholding 2

See merge request Librem5/developer.puri.sm!103

Update hardware information

See merge request Librem5/developer.puri.sm!104

DON'T PANIC

- Split devkit and phone
- Use consistent capitlization
- Move CPU/RAM/storage to top
- Fill in some details and remove duplicates

As follow ups we might want to split out individual sections and add
photos.

Uncomment hardware list by moving reST comment

See merge request Librem5/developer.puri.sm!98

Update the qemu documentation with some minor fixes and hints

See merge request Librem5/developer.puri.sm!95

Add a phone section, tidy up existing sections

See merge request Librem5/developer.puri.sm!99

Dev kit handholding

See merge request !97

Caution: this procedure is written with an image that a minority of dev kits ship with

Tidy up new devkit information

See merge request Librem5/developer.puri.sm!96

Finish the sentence about tools.
Make it clear that flatpaks are just one delivery method.

Moving the inline XML into a separate file.

Move details about software into the Software Reference chapter.
Fix the Hardware Reference identifier.