This PR reworks the web layout so static files can be provided and
a "themes" directory to allow a certain degree of control over logos,
styles, etc.
This PR does NOT add general support for frontend customization,
only enough to allow us to start exploring theming internally.
The dex binary also must now be run from the root directory since
templates are no longer "compiled into" the binary.
The docker image has been updated with frontend assets.
Add a small program to iterate over the templates directory and
generate a go map of name to file data. This is so we can compile
these templates into the dex binary instead of requiring files on
disk.
Also add a Makefile rule to do this automatically.
It's not clear that the best way to manage clients is through a
gRPC based command line tool. For example we may explore an admin
dashboard and enable bootstrapping through static clients.
For now use static clients while we hold off on a more concrete
proposal.
