Show precedes/follows and blocks/blocked relations on the Gantt diagram (#3436).

Based on Toshi MARUYAMA's patch.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11118 e93f8b46-1217-0410-a6f0-8f06a7374b81
Use JSON so we don't have to parse data-rels manually (#3436).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11119 e93f8b46-1217-0410-a6f0-8f06a7374b81
Only process issues that have relations.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11120 e93f8b46-1217-0410-a6f0-8f06a7374b81
Store the other issue in a variable (#10916).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11121 e93f8b46-1217-0410-a6f0-8f06a7374b81
Login link unexpected logs you out (#12611).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11122 e93f8b46-1217-0410-a6f0-8f06a7374b81