Fix measure upload dialog when no measures are loaded

#### Story ####
- https://www.pivotaltracker.com/story/show/63216448

#### Notes ####
- Marked <code>measures</code> collection's <code>_fetched</code> field with <code>true</code> value after bootstrapping measures in application.html.erb
  - This prevents the collection from fetching, so all server errors are prevented, as well.
- Alternative solutions require removing <code>url</code>, reworking collection implementation to prevent undesired loading/fetching, or reading <code>length</code> field off of the collection