Make warnings / needs-attention counters clickable in AppLauncherView

Convenience links to relevant tasks/audits/reviews (Maniphest, Differential, Audit)

![phabricator applicationlaunchview - clickable attention count](https://f.cloud.github.com/assets/1309249/2233646/6c01c566-9b2c-11e3-9762-eda860bc200f.png)


Couldn't test it on my Windows due to memory alloc errors (not related to this patch).

Thanks to epriestley (#phabricator, irc.freenode.net) for helping me out!