Bug 10442: Remove references to non-standard "error" class

The CSS for <div class="error"> is obsolete and should not be used. This
patch removes the definition from the main CSS file and corrects
instances of its use in the templates to the standard <div class="dialog
alert">.

To test:

- In Acquisitions -> Late orders, locate an order from a vendor which
  doesn't have an email address. Selecting that order and clicking
  "Claim" should trigger an error dialog, "This vendor has no email." It
  should be styled correctly.

- With  AcqCreateItem set to "when placing an order," add to an existing
  order using the "From a new (empty) record" option. Add two items with
  identical barcodes and submit the form. A error should show at
  the top of the page.

- With AcqCreateItem set to "when receiving an order," receive an order
  and add two items with identical barcodes. Submitting the form should
  trigger an error message at the top of the page.

With the remaining cases I don't know how to trigger the errors in
question, so a visual check of the changes may be required:

- Administration -> Funds -> "You are not authorized to modify this
  fund"
- Administration -> Search engine configuration
  (/admin/searchengine/elasticsearch/mappgings.pl) -> Various
  modification errors.
- With the  AutoEmailOpacUser preference set to "send," adding a patron
  without an email address can trigger an error, "This member has no
  email."
- With plugins enabled, and installed, there are error messages
  displayed under various circumstances.

Signed-off-by: Andrew Isherwood <andrew.isherwood@ptfs-europe.com>

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>