add dzen into header
fix forum layout
fix forum post form
Change functional for rnd messages in header

all made via app header_messages
new messages add in admin panel
return rnd message based on it weight
change class Header_message to HeaderMessage
remove weight
and etc according notes
change method rnd
Merge pull request #221 from user783/dzen

Re #217: Add Python dzen into header
fix hreader messages
fix search by forum, fix #223