Improve Production mode build

[knutole]

When switching to prod-mode, it's necessary to ensure that latest wu has been built. This does not happen automatically now - a manual ./build.sh is necessary (as well as manually updating current version).

Need to streamline this process.

• make switching from dev to prod mode as simple as possible, and with only one switch. (Currently two lines must be changed in .yml file
• ensure latest wu is built when starting up prod mode. must check which version is latest, and build if necessary. perhaps belongs in restart.sh script.
• perhaps tag versions on github with :latest and always build from that