Adds CustomField#group_statement.
Use JQuery Dialog (#11445).
Use JQuery Datepicker (#11445).
JQuery in, Prototype/Scriptaculous out (#11445).
Fixed that settings raises an error if not trackers exist (#11467).
code layout cleanup lib/redmine/helpers/gantt.rb
replace tabs to spaces and fix indents at lib/redmine/helpers/gantt.rb
code layout cleanup app/views/gantts/show.html.erb
code layout cleanup test/unit/lib/redmine/helpers/gantt_test.rb
add copyright statement to test/functional/gantts_controller_test.rb
