Call testing repository's main branch 'master' instead of 'tested'

Calling it 'tested' means the repository's HEAD (which is a symblic
reference to refs/heads/master by default) is a dangling reference.
Fix JavaScript error on /home when user has no filters

The inline script that defines 'count_matched_files' is only generated
if the user has filters, so need to make sure the variable is defined
before using it.
Upgrade to jQuery 2.0.0 and jQuery UI 1.10.2

Also remove jquery-tooltip plugin and use the tooltip functionality that
is included in jQuery UI.  The API was slightly different so some code in
client-side scripts needed to be updated.  (The tooltips on comment
markers got a bit of a face-lift in the process.)

Also change code that manipulates the disabled state of form controls to
use

  obj.prop("disabled", true|false)

instead of

  obj.attr("disabled", "disabled")
  obj.removeAttr("disabled")

as suggested in the jQuery 1.9 upgrade guide.

Also add the style-sheet jquery-ui-overrides.css to override specific
styles in jquery-ui.css.  For now, it effectively reverts a change in
jQuery UI relative the previously used version that changes the font
used by widgets ("Verdana" had been removed from the list of fonts.)
Add administration tutorial
Add system customization tutorial
Fix linkification of diffs "A..B" where A/B are SHA-1s

Linkifying A as a plain SHA-1 took precedence, so the diff reference
became two commit links to A and B with ".." between them.
Add basic linkification test
Only call LinkType.linkify() for words matching LinkType.fragment

This essentially moves this check out of each link type's linkify()
implementation, thus making the code simpler (and implementation of new
link types less error-prone.)  It also matches the documentation of
linkification customization in tutorials/customization.txt.
Support link types with leading non-word characters better

Requiring a word-boundary before a link "word" means that link types with
leading non-word characters must be immediately preceded by a word
character, which is unlikely to be the case.

Relax the requirement by requiring either a word boundary before the link
"word" or that the link "word" begins with a non-word character.  (Such
a relaxation was already in effect, but only for a select few non-word
characters.)
Add test for linkification customization
Fix use of super() in base.ImplementationError sub-classes
Add documentation/tutorials.txt advertising the tutorials