Updated AddonManager userscripts to match other addon-types

It always bothered me that the add-on manager for userscripts is a little bit different then the other add-on types. 

So today I updated the:
* _scripts listing_ - Added the following:
 * __More__ - Added the `More` link, linking to the scripts detail page.
* _details page_ - Added the following meta:
 * __Creator__ - Shows the author when `// @author` is defined in the userscript. When homepage (see below) is defined, creator will be linkable.
 * __Homepage__ - Adds link to scripts homepage when `// @homepageURL` is defined in the userscript.
* _context-menu_ - Right-click on an userscript. Added menuitems for:
 * __Show More Information__ - Opens the details page. This item is default behavior, so it's bold.
 * __About__ - Opens the about dialog.

No localization updates, as all are from Fx own localization.

Maybe TODO's:
* Add more metadata's that have same attributes in Fx (like `// @supportURL` && `// @contributionURL` and more).
* Add list of all remaining metadata's (e.g. `// @grant`).
* Minimize menuitems `Execute (first|sooner|later|last)` (maybe a sub-menu).