Better marker styles.
Add markers to elements with accesskey or clickable class.
Do not add markers for elements with 'button' in class list.
Add marker to current image to allow zooming in and out. Fixes #103
Implement per-site command disabling.
Show/hide TreeStyleTab tabbar command
Merge branches 'feature/better-styles', 'feature/clickable-accesskey', 'feature/imgzoom', 'feature/location-disable' and 'feature/treestyletab' into mine