Add Help link (F1)

[PropGit]

Add a Help menu item that links to an on-line resource (to be opened in Chrome).

Parallax will maintain the linked page to provide the help resources needed for users. Initially, this will be a PBASIC Language Reference.

For this release, the link should be: http://www.parallax.com/go/PBASICHelp

[PropGit]

As discussed in our meeting, we can not add this as a UI element currently.

Please add this as a link that is activated by the F1 key.

[PropGit]

Verified done.

Note: security policies prevent linking programmatically. The solution is instead to display an overlay with a link to the resource that the user must then click on. This turns out to not be too disappointing here because we can provide multiple resource links on the overlay and limit the help menu to a single menu item.