Analyse and update provisioning script

The provisioning script seems a bit funky - it pulls dotfiles and such atm. It's also pretty old - it'd benefit from someone checking what's necessary to get a pi up and running and updating the script accordingly.

[kragniz]

These are really old - use the deployment and provisioning scripts from dewi instead https://github.com/abersailbot/dewi

[NicholasRostant]

@kragniz How up to date are the Dewi ones? (And do they also include all your dotfiles?)

[kragniz]

iirc working as of the last commit, which was sailbot 2017

[kragniz]

they still need an update, but dewi's going to be a better base to work off (it doesn't include any of my dotfiles)