Build in progress indicator

[dekz]

0xProject/0x-launch-kit#5
0xProject/0x-launch-kit#9

Users are reporting errors when it is simply taking longer than expected to build the front end. At least for the first time it takes a while and incremental builds are a bit quicker.

It would be good to have a clear indication of when the system is "Ready".

Some thoughts are a default nginx page which gets replaced when the build is finished.

Better indication in the docker-compose flow to indicate that a build is still on-going. Currently it just says it is creating an optimised build, which gets hidden by other logs of starting containers.