Rework forum structure

[user0]

Forum structure is not clean enough.

Suggestion
Rework forum structure, especially XnViewMP section:

1. Announcements
   • move them one level up, into the new 'MP - Announcements' section.
     As they do not belong to 'General Support', but take much screen space there.
   • lock this new 'MP - Announcements' section, so users cannot write there.
2. Sticky topics
   • move them from general TOPICS section up to the top, into the new STICKY TOPICS section.
     So they are visually better distinguished from conventional posts.

Mockup
based on XnViewMP section

forum_structure.png