Clicking 'Force Build' gives no feedback to the user

[kaiwren]

Clicking force build currently has no immediate visible effect.

Only when the build actually starts and the page self updates (which even with a single build can often take > 10s) does any visible change occur.

There should be an additional build state of 'queued' to handle this situation.

[srushti]

Added a little bit of text to the force build button if a build is currently queued 83f4cf7.