Make the "Install Dashboard" flow smoother
Instead, allow users to install things to any valid target (home, favorites, portals, projects). This also provides URIs like dashboard/install/1/home/personal/ which allow you to link users to an "install a dashboard" page; this may or may not get used.
Test Plan: Installed dashboards on home, favorites, projects, and portals.
Reviewed By: amckinley
Maniphest Tasks: T13272
Differential Revision: https://secure.phabricator.com/D20364