debug ajax error
fix typos in end user strings #2675
working site registration ajax form submit & overlay

#2675

### Changes
* fix misc comment syntax & missing var declaration in
vsite_access.module
* fix markup for success & welcome message
* add helper css classes "os-green-button" and "os-blue-button", in 2
separate css files.

### Question
* better place than os_help.css for new blue button rule? i didn't find
any other openscholar-specific css files loaded in the overlay for the
default admin theme.