gluon-autoupdater: no need to provide a default config just to delete it in the initial script
gluon-location: move information to /etc/config/gluon-location
gluon-mesh-batman-adv: move wifi config to invariant
gluon-simple-tc: add missing defaults on every upgrade
gluon-autoupdater: Refactor code.

Move building blocks of the update into seperate functions.
gluon-autoupdater: Less global variables.

This also removes the need for the cleanup function. Instead the cleanup
code is moved in place.
gluon-autoupdater: enable list of mirrors for manifest and firmware.

Instead of a single url this patch allows to have a list of urls. So in case
of network instability a router can still reach local mesh-cloud server to pull
a update from. In this stage the autoupdater simply tries every mirror until
one passes all tests.