tigefa4u projects Trac

Reimplemented the quickjump feature by reusing the available TracLinks syntax.

First, this avoids the duplication of the regular expressions for tickets, wiki page names, etc.
Second, we gain the ability to quickjump to log ranges, revisions defined using `rXYZ` (#2881) and all the link resolvers that were not previously considered (attachment, query, log, etc.)

Likewise, this automatically extends the quickjump feature for TracLinks defined by the `IWikiSyntaxProvider` plugins (provided they return `Element`s objects with a `href` attribute, typically `html.A(href=...)`).

This required a small refactoring of the Formatter, a step in the direction of separating the parsing and the formatting phases in the Wiki engine.

Follow-up to r3348, need to be able to call get_mimetype without a content argument.

The !WikiProcessors can be user configurable as well (follow-up to r3345)

Our pysqlite2 cursor wrapper returns None istead of [] from fetchall to indicate an empty result set. This is non-standard and makes no sense. This fixes #3193.

WorkFlow: Merged log:trunk@...:3345

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 :)