Displays navigable path name on file and folder pages.

This change displays the name of the source file at the top of the
page. The name can be copy/pasted directly into an editor or anything
else to get to the file. Fixes
https://bugzilla.mozilla.org/show_bug.cgi?id=758628
The individual components of the path can be clicked on for
convenient navigation.
Merge master in before I try to polish up clickable pathnames.
Polish pathname display for release.

* Use just '/' instead of os.sep. If we ran the server on Windows (which wouldn't work anyway), the path would come out as /treename/source\some\path.
* Tweak some naming, style, and spacing.
Add tests for linked_pathname(). Refactor it to be more testable.
Fix more whitespace, and improve more naming.

I see Noufal realigned all the template var dicts, giving them wider columns to accomodate his long key name. Per PEP 8 and my preference, cut all that stuff down to single spaces so it's easy to edit in the future.
Merge pathname breadcrumbs. Fix #130. Fixes 758628.
Fix tests on Python 2.6.
- logging.StreamHandler doesn't support a named parameter "stream"
- The workaround for errors from setuptools needs to be updated
  to use concurrent.futures instead of multiprocessing since the
  tests were changed to use concurrent.futures.
Read and print the build log when *not* in verbose mode. Clean up style.
Merge in jcranmer's dummy-merge of prod, so the hg mirrors pulling prod will happily fast-forward to master. We should fix (or get rid of) the mirrors when we can.

The only change is #ifdef-ing out some noisy "Unprocessed kind" build output.
Add a --verbose option to dxr-build so buildbot doesn't get bored and abort our jobs.

buildbot needs output every 2 minutes or hours or something.
Rewrite readme intro for accessibility to new folks. Fix #139.
When opening stdout as a file for verbose logging, use write mode instead of the default.
Prepend wwwroot to breadcrumbs
Extension search now matches the whole extension. Fixes bug 848485
Merge fix for searching by extension. Fix bug 848485.
Add support for searching for namespaces and namespace aliases.
Add support for building against clang version 3.3.
Create a CLANG_AT_LEAST macro and use it for version detection.
Fix search_url in server response
Rename RemoveTrailingColonColon to removeTrailingColonColon
to indicate that it is a private helper method.