Merge pull request #129 from doopl/master

Icons
Note graphics sources and credit Android Asset Studio.
Merge pull request #133 from doopl/master

Make game titles more prominent in chooser
Sharper icons for the chooser (fix #132).

This leaves the "net" icon in the action bar at the wrong size, but that'll
be replaced with a new app icon anyway under #116.
Merge branch 'master' of git://github.com/chrisboyle/sgtpuzzles
Tidy a bit in preparation for docs update.
Update docs (fix #130).
Unruly: sticky cursor, follow touch (fix #135).
Fix #131 by adding a note about right-click to every controls section.

Any other docs change would be too disruptive to merges of documentation
from upstream, and thus should be made upstream in a multi-platform way
or not at all.
Some more lint and tidying.
Remove more unused lines/icons; stop lint thinking that showAsAction=always is used unconditionally.
Allow starring games in chooser (#134). Needs some polish, see TODOs.