Add accesskey functionality to pledge editor page

[rakess70]

My wife requested accesskey functionality for save, save and add, ad cancel buttons. to make data entry faster for those adding in deposits.

I added those locally to my copy and she said it works great.

Most time when accesskeys are added the letter used is underlined on the botton on screen to indicate a accesskey.

since the text for the button is called from the gettext POEditor I am not sure how that might work.