Removed IssueStatus html_color attribute.

Issue list colorization can be done using a custom theme. Each row is given a class that correspond to the issue status (eg. status-1 where 1 is the status position).

git-svn-id: http://redmine.rubyforge.org/svn/trunk@881 e93f8b46-1217-0410-a6f0-8f06a7374b81