New setting added to specify how many objects should be displayed on most paginated lists.

Default is: 25, 50, 100 (users can choose one of these values).
If one value only is entered in this setting (eg. 25), the 'per page' links are not displayed (prior behaviour).

git-svn-id: http://redmine.rubyforge.org/svn/trunk@1026 e93f8b46-1217-0410-a6f0-8f06a7374b81