Fixed Issues/Bugs

IMPORTANT: Blocking performance problem resolved (can't save user story, bug or request on large database).

#12238 Images uploaded in 2.11 are not available in FCKEditor WYSIWYG after update to 2.12.
#12262 Burndown Chart: posting time to the past issue.
#12266 Burndown Chart: design improved.
#12300 Burndown Chart: there is no Ideal Line on chart, if end date is a weekend.