* updated & cleaned up examples some more
* added features/feature flags to 'common' example boilerplate
* moved xpbd physics to common, behind a flag too
* updated xpbd example
* updated code for bevy_asset_loader changed api
* more cleanups
* updated dependencies
* updated code where relevant
* temporary removed editor
* attempting to tweak lighting/camera proxies to match Bevy's new defaults
* updated assets where relevant
* still wip, as bevy_xpbd is not yet updated for 0.13
* all work except the above & save/load