Treat empty inputs as non-errors in two wiki validators.

If VLength (or its subclass) gets an empty input, by default it will set
an error state. This error state now has a code param, which causes wiki
code to treat it as fatal. This change disables the empty error in two
places, when appropriate.
Prevent inner form throbbers when parent element is working.

This keeps the copy and rename form throbbers from showing when an
operation is in progress on their parent form.
js.py: Only include permissions strings if referenced.
Make reddit-init.js a LocalizedModule.
Make user page multi list multi-column and summarized.

Borrows a modified version of r.ui.Summarize, originally written for
another project by @spladug.
Consolidate listing chooser LESS code; shorten variable names.
Listing chooser collapse grippy usability improvements.

* Increase thickness of grippy.
* Grippy icons with arrows pointing in the direction of show/hide.
* Invisible extra width for easy targeting.