tigefa4u projects Trac

Refactoring of TracCrossReferences: create `trac.xref` module

The cross-referencing facility has been separated from the TracObject.

In the `trac.xref` module, there's now a separate file for the Web UI
and the macros (that's fine, as there will be more macros in the future).

Finally, the API for the xref has been simplified and the documentation
has been updated.

workflow:

* Fixed custom field display in newticket.cs
* Ticket creation now passes through the workflow system, allowing field filtering and validation.

workflow:

* Fix for some badly formed HTML introduced in form_control()

workflow:

* Updated unit tests to work with new API.

workflow:

* Merged notification changes from trunk.
* Added trac.ticket.field.

New email notification subsystem:
* Support of Base64, QuotedPrintable or No encoding
* Support for Cc: or Bcc: copy
* Address #1754, #2014 #2309, #2408, #2424, #2434, #2457
Creation of email notification unit tests
* 7 basic unit tests, using a local SMTP server

Ported [2797] to 0.9-stable ''(fixed pretty_size)''

`pretty_size` now shows the correct size for 512 bytes files. Closes #2621.

sandbox/notification: remove stmp test server, fix up copyright notices

sandbox/notification: proper split of /trac/Notify.py, same features as [2787]