Fix the overflow problems in project jump
Some rounded in Redmine are missing overflow:hidden; parameter, which results in corners of child menu elements to stick outside of the parent box which contains them, this results in rounded element, not to look so rounded after all.
This patch fixes it and in addition, sets border radius to 3px like everywhere else
P.S. 1 ticket per issue, but this was way too small of a change, with micro issues which are kind of related, didn't want to open a separate issue, sorry, but you will insist, I can separate it ;-)