Otherwise, you could load a giant scene, close the browser, and be stuck with
it forever!

This reverts commit 4c58eb9b94.

Still very rough around the edges...

The defualt view was being referenced.

The viewport attribute is now set, which should make mobile devices show it a bit
more correctly. I updated the bottom-names to be placed properly on mobile.

The preset-size buttons were causing the values for
the default view of an entity to be shown, even if
another view was currently selected.

Very large entities are confusing to add - they appear for a brief moment
and then grow off the screen. This shows an arrow if an entity is at least
ten times taller than the viewport.

This also probably fixes bugs with wrong z-indexing for fresh entities

Entities are only selected after creation if requested - this was
taking a lot of time, and was pointless. The tick-drawing function
doesn't read calculated styles as much now, but it still forces
a reflow when setting the font, weirdly.

Previously, every call to updateSizes() would update every entity. Now, entities
can be marked as dirty, and updateSizes can be called such that it only affects
dirty entities. I changed a few calls to updateSizes to take advantage of this,
but others can probably be optimized too

This was, previously, explicitly handled with a factor of (1 / (1 - x)).
I just regex'd away these factors, so there are probably a few errors.