I did a full `cargo upgrade` and fixed what it broke:
* a couple things for the latest protobuf 3.0 alphas
(note alphas don't promise API stability)
* new minimum supported Rust version
This should have some other nice effects: parking_lot now uses inline
assembler, tokio has gotten faster, etc.
I'm tired of all the boilerplate, so use the new
GPL-3.0-linking-exception license identifier instead in all the server
components.
I left the ui stuff alone because I'm just going to replace it (#111).
Add a checker for the header because it's easy to forget.
Besides being more clear about what belongs to which, this helps with
docker caching. The server and ui parts are only rebuilt when their
respective subdirectories change.
Extend this a bit further by making the webpack build not depend on
the target architecture. And adding cache dirs so parts of the server
and ui build process can be reused when layer-wide caching fails.
