(#1661) - use task queue for IDB for IE

Adds a task queue for all create/destroy
operations on IDB databases, because apparently
IE 10 and 11 can't function correctly if there's
any overlap between any destroys/creates (even
from different databases).

Also apparently you can't have two databases
with the same name open at the same time,
so we have to cache this.  Unfortunately,
Chrome prefers the opposite, so for the time
being I'm using user agent sniffing to
exclude Chrome from the caching.  If anyone
can think of a better idea, I'm all ears.