keep track of the expiration initially set for a view

keep track of the expiration initially set for a view so that we can keep using that when it's refreshed.

for example pulltorefresh just does `Andamio.views.refreshView(Andamio.views.currentView, null)` which will cause it to use the default cache TTL, even for parent views.
the result is that if you pulled to refresh once, it's cached for a week in jaws ... forcing you keep using pull to refresh ... :(