Merge pull request #1 from sagittarian/controller-string

Change the sprints controller to be a slash-prefixed string
Context menu & issue sprint drop-down fixes (for locked sprints)
Merge pull request #3 from sagittarian/context-menu-and-issues

Context menu & issue sprint drop-down fixes (for locked sprints)
some alternatives
fix sortable after contax menu
Allow sprints to be shared with subprojects

Nearly identical logic to version sharing.
Requires plugin migrations (rake redmine:plugins:migrate).
fix typo
Merge pull request #4 from sagittarian/sprint-sharing

Allow sprints to be shared with subprojects
fix migration
Change 'descendants' sprint sharing type to 'subprojects'
Use all shared sprints when determining the last sprint