[FEATURE REQUEST] Select all button on the 2nd software selection menu

[darigovresearch]

Very often when installing on a new Pi we want to install all the apps on the 2nd menu apart from one or two apps. Unfortunately currently there is only a "Select all and continue" button and not a "Select all" button.

This would be really helpful as otherwise the user needs to select almost all the apps which can be a little difficult if the user is trying to install it via a VNC viewer from a tablet. There is also space for a fourth button in that specific menu.

Was going to make a pull request but bash is not our specialty but happy to do so with some guidance on where to insert what in the relevant sections of the codebase.