API: Column selector now allows `{integer}:visible`

- This is an alias of `{integer}:visIdx` which should be a little easier
  to remember.
Build: Build repo syncing

- The `make.sh` script now has a `sync` option which, when run, will
  run through the commits from the last sync commit in the build repo
  and the HEAD (this is done in the src repo) and built the build repo
  for each commit. If a change is needed (i.e. a file has changed in the
  source repo which effects something in the build repo) the commit
  message from the source repo is used to commit to the build repo,
  keeping the two in sync.