Prevent stack overflow if adapted command calls own methods.

This changes the adapter to aggregate the adapted command rather than inheriting from it because the latter can lead to a stack overflow if the superclass calls the adapted method in its implementation.  In other words, the adapter method would delegate to a method of the inner which, via virtual method dispatch, ends up delegating back the the adapter method.
Added 'About Swish' box to Explorer Help menu.
Improved git version display.

Longer hashes.  "unknown" as fallback.