Make responsive work.

Also make base classes all inherite from C. Make export paths work with
CSS, so they won't save inside source tree. Now
~/Desktop/Xierpa3App/sitename is used.
Get responsive CSS working again.

Seems to work mostly on the DbD site. Not yet on the
HelloWorldResponsive site.
Add web fonts to column site example.

Some more cleaning of C references, change to self, not all main base
classes inherit from C.
Get responsive CSS generator to work again.

Generating @media CSS is much cleaner now. Still needs checking on
duplicates, but for now it works. Changed constants M_MOBILE_MIN, etc.
now also includes M_TABLET_MIN and M_TABLET_MAX.
Add some web fonts to example sites.
Updating TODO list.
Extended DbD Hello World example article with responsive site version.
Adding to TODO list.
Add simple type specimen as example site.
Add meta description and keywords.

Add getDescription and getKeyWords to adapters. Add to blurb adapter
and to DbD adapter.
Clean obsolete @media methods from SassBuilder. Rename M_MOBILE
measures to make more consistent with screen ranges. Start of
SimpleWebsite example class.
Starting SimpleWebSite example class.
Merge branch 'Responsive'