Restore home menu order

[u-foka]

• Added a new field to external apps header (desired_menu_position) and bumped the header version to 3
• Added the new field to all external apps (defaulted to -1: (no desire) except for remote that goes to index 4 on the home screen (also had some cosmetic changes in some of the main.ccp-s)
• Update the python script that creates the ppma-s to account for the new field in the header
• Applied the desired position to the apps when populating the screen
• Also had some optimizations in btngrid to only update the items once, instead of each icon added, and potentially eliminated a copy (might have already been optimized out by the compiler)
• Moved the missing ext apps notice on the home screen to index 2 to preserve the position of the rx and tx submenus

Currently only external apps have desired locations, we could add it also for the standalone ones in the future.

Current menu layout:

• Built in apps (might be mixed with external apps that has desired position)
• i2c module app
• external apps (without a desired position)
• standalone apps

Closes #2374

[gullradriel]

Looks good to me, great job @u-foka !

[gullradriel]

Currently only external apps have desired locations, we could add it also for the standalone ones in the future.

Now I want to have this too, maybe in another PR. Should I open an enhancement issue ? ^^