Forum rules updated

[Spack]

I've made a small amendment to the forum rules (cheers KMB), and moved it to it's own Announcement post here The Site forum. I've also added a Forum Rules link to the forum menu at the top of every forum page.

I've create a new Helpdesk forum for posting about problems with the site, so this forum is now for suggestions for new features and for me to announce new features.