Add preliminary support for Android devices

Fixes for touch events and scaling issues.  More on this later.
Merge branch 'master' into debian
New snapshot
Dashes (hlines) are optional to separate slides

Split slides before headings, no need to use dashes to separate slides.  This
change should be backward compatible, since using dashes is optional and causes
no harm.
Document new features + cosmetic changes in documentation
Merge branch 'master' into debian
New snapshot