Merge lp://staging/~adeuring/launchpad/bug-768443 into lp://staging/launchpad

[r=gmb][bug=768443] new cached property Person.administrated_teams; Person.administrated_teams used in lp.bugs.browser.structuralsubscription.expose_.*_to_js() in order to avoid multiple calls of Person.getAdministratedTeams()

This branch fixes bug 768443: ProductSeries:+index timeout with many releases

The reason for the timeout are many calls of Person.getAdministratedTeams() in lp.bugs.browser.structuralsubscription.expose_user_administered_teams_to_js() and lp.bugs.browser.structuralsubscription.expose_user_subscriptions_to_js()

These functions are called in lp.registry.browser.productseries.ProductSeriesView.initiakize() and in lp.registry.browser.milestone.MilestoneView.initialize()

One OOPS had more than 90 calls of getAdministratedTeams(); with an "SQL time" of 80..200msec per call this is an obvious cause for the timeouts.

At first I intended to cache the query result inside Person.getAdministratedTeams() but got scared when I noticed that this method is also used in security.py -- if the affected checkAuthenticated() method is called in a method where team memberships are changed, we might end with an invalid permission check, so I added the somewhat redundant cached property Person.adminstrated_teams which is now used in the affected functions expose_.*_to_js()

tests:

./bin/test bugs -vvt test_expose
./bin/test registry -vvt test_person.TestPersonTeams

no lint