Added SparkAction classes, key bindings, and action methods.
Implemented annotation selection offset and abstracted click handler to use same selection mechanism (selectMarker) as orev and next methods (selectMarkerFromCurrent)
Fixed a couple of bugs and changed visibility.  Fixed a missing rename
Reorganized and fixed situation if currentMarker == null (before a marker is clicked on)
Added todo
Changed names s/[Aa]nnotation/[Mm]arker/g and switched to using defaultBinding instead of platform specific
Inlined next and prev marker calls
setup key bindings to loop current marker
Merge pull request #664 from dart-lang/minimap-keybindings

Marker key bindings