Try to update texts where possible.

The new code matches up existing texts for the same element and just
assigns over the ID instead of creating a new text if one already
existed and we're "overwriting." If there aren't enough old texts,
new ones are still inserted, and if there are too many, the leftovers
are deleted.

This results in much less churn for the common case of one, a few, or no
edits to element texts, all scenarios which currently cause the deletion
and reinsertion of all the texts for the item.
Fix #512, escape error messages, backtraces.

Use htmlspecialchars here to allow the error page to be used without
Omeka being loaded.
Move admin pagination to views for public to use as well.
Make secondary-nav id into a class.
Wrap the error message summary.
Move to a joins-only simple search for items.

See #518
Remove stupidity from last commit.
Clear out attached items when deleting collection

Fix #507.
Fix item_type_id post value filtering.
Bump version to 2.0.3.
Fix #522
Fix #527, check filter helper find() results.
Update Transifex config.
Pull from Transifex.
More forceful pull from Transifex.
More Transifex.
Update submodules.
Set version to 2.1-dev.
Merge branch 'stable-2.0'

Conflicts:
	bootstrap.php
Fix #530, remove dormant users/browse form.