- Propagate size limits (including detecting memory limits from GD) down to the
Flash so that we don't even start uploads that won't work
- Improve the error messages to be more user meaningful and provide links to the
codex for errors
- Tell the user up front what the file size limit is.
Fixes#1638
clarity, since it only limits concurrency not the number of actual uploads.
Move the default-setting code into the upgrader so that we avoid
creating the variable as a side-effect of the view (personal
preference to avoid side-effect code since it's led to problems in the
past).
