Documentation: simplify structure

[M-a-r-i-a-n-n-e]

Currently, I click on several pages in the documentation until I find what I'm looking for (e.g. looking for development hints on the setup page and not on the development page).

I suggest to:

• Move the development part (the one under the caption, currently without an own headline) from the "setup" to the "development" page. Also move the translation in the *.po files.
• Split the page "resources" and put the "software" to the "setup" page and the "hardware" to a (future) "parts list (BOM)" page.
• Rename "setup" and "setup (LoRa)" in a way that their meaning becomes clear.. maybe "Setup (WiFi)" and "Setup (LoRa)". Maybe some general hints can find their way to a "Setup (general)" page.
• Move the BLE bluetooth section from the "usage" page to a single "Setup (BLE)" page.

What do you think?