[skip ci] automatically save layer settings in local storage and reload them on startup
save layer settings per user [skip ci]
stashing changes [ci skip]
[ci skip] session clear only removes 'our' data, handle default keyword (manual backport)
implementation done, added blank background [skip ci]
[skip ci] correctly localize solid white base map
[skip ci] improve base layers configuration
[skip ci] ensure backwards compatibility
[skip ci] refactor property names to sthing more meaningful, better error checking
[skip ci] merged experimental/custombaselayers into master
[skip ci] merged localStorage improvements