(minor) stick closer to jQuery.Widget implementation of snakview disable/enable

snakview will now allow option( 'disabled' ) for checking whether snakview is currently disabled.

- patch set 2: Removed obsolete _disabled attribute.
- patch set 3: Extended documentation

Change-Id: Ia6a7ee9088c14f3c585af2f9c9f9524e2e996874
Merge "(minor) stick closer to jQuery.Widget implementation of snakview disable/enable"