tigefa4u projects Trac

Refactoring of the known MIME type associations.

This is now configurable, in the `[mimeviewer]` section:
* the `mime_map` list is used for declaring new MIME types
and enumerating associated keywords or file extensions
* additionally, one can set `enscript_modes` and `silvercity_modes`,
which are lists of MIME type, mode and quality ratio associations
for those renderers.

This can be used for:
* assigning extra keywords/file suffixes to an
already known MIME type (#1283)
* adding support to new languages (#2874)
* force usage of Enscript instead of SilverCity
(or vice-versa) by overriding the default quality ratio
* adding extra languages to customized SilverCity (#2198)

Example:
{{{
[mimeviewer]
mime_map = text/x-idl:ice,text/x-dylan:dylan:dyl
enscript_modes = text/x-python:python:5,text/x-dylan:dylan
silvercity_modes = text/x-java:Java:5
}}}

Added some unit test for `get_mimetype` before doing a bigger refactoring.

Make it possible to escape the bold/italic formatting using the usual "!" prefix, and simplify the code accordingly.

Move some of the trac.util functions in dedicated modules:
* trac/util/text.py for the unicode and text formatting utilities
* trac/util/datefmt.py for the date formatting and parsing utilities
* reorganized a bit the remaining functions in __init__.py
1. algorithmic functions
2. os/sys utilities
3. crypto utilities
* adapted all the `import` statements for the above changes
* fixed a few remaining !TracError import from `trac.util`
(should be from `trac.core`).

Follow-up to r3339, taking into account r3241... Thanks cmlenz for being vigilant :)

Various small clean-ups in the Wiki formatter:
* break paragraphs also for the `system_message` div elements
* when calling a macro, don't scan the list of macros twice
* !InterWikiMap can be used as a dict
* lots of small improvements to the documentation
* /me added as one of the author/maintainer for the wiki code

Set a dummy log handler in case the `log_type` is not specified or not known. Fixes #3148.

Email notification: do not attempt to send a notification if no valid recipient has been found. Should fix #954
* add a new unit test

Email notification: document the new options `smtp_default_domain` and `use_short_addr`

Email notification changes:
* ensure all physical lines in a message end with the '''CRLF''' marker, to fulfill RFC2822 requirements.
* introduce support for TLS-enabled STMP server
* deprecate the "maxheaderlen" configuration option