Updated "gashp" alias to be a function with multiple stash prompt support.

* If multiple stashes are detected, it will prompt for stash selection.
* If a single stash is detected, then it will auto-pop the stash.
Updated "gashs" alias to be a function with multiple stash prompt support.

* If multiple stashes are detected, a prompt is presented.
* If a single stash is detected, the last stash is shown.
Updated "gashd" alias to be a function with multiple stash prompt support.

* If multiple stashes, then a prompt is presented.
* If a single stash, then the single stash is dropped.
Refactored the "gashl" alias to a function.