Translation, settings for minimum word length and couple of security fixes

+ Added russian translation.
+ Added html symbols filtration (so we can avoid problems with issue called "&lt;script&gt;alert('xss')&lt;/script&gt;" and other tags)
+ info log -> debug log
+ Minumum word length made configurable (for example: for russian language we need more than 2 symbols) 
+ Added rakefile and test for the index action of search_issues_controller
+ Issues search should not violate issues privacy (such as 'private' issues made by other users)

Tested with redmine 1.4.4 + ruby 1.9.3-head

p.s.
  I can revert some changes if something gone wrong