Extract Guide TOC creation to a class.
Allow linking to named anchors inside guides.

Created GuideAchors class which transforms the hashes in links
and ID-s in anchors so they don't interfere with Docs app #!-navigation.

Relaxed the pattern matching of guide URL-s in Docs app and added
support for navigating to <a name="..."> anchors.
Create human-readable TOC links.

Instead of numeric myguide-section-3 we now get derive heading ID-s
from heading text.  For example: myguide-section-getting-started

Also added testsuite for GuideToc.