Reduce the finder proxy cache time to 0.5s
Reduce Latest Download cache time

And tidy up file
Set the default proxy cache time to 2s
move the kQSDefaultProxyCacheTime definition to the header

…so other proxy objects can use it
generalize getting info for other proxies
respect the cache time of the passthrough proxy

If there isn’t one, use the default.
adjustments to failDate

* It only gets used in a class method, so it doesn’t need to be an
iVar. It’s declared locally.
* Made it static
* Sync the timeout for failure with the default proxy cache time.
They’re not the same thing, but they should both be updated as hardware
gets faster.
make Current Selection more efficient

* only get information for the current application once
* alter the order when getting types: types from plist, fallback to
string, types from provider → types from provider, types from plist,
fallback to string
* eliminate the poorly named passthroughProxyInfo class method
make Finder Selection proxy refer to symlinks

…instead of returning the path to the source file(s)

fixes #1729
treat QSGlobalSelectionProvider as a singleton

allows us to use instance variables to keep track of things instead of
static locals
Merge pull request #1748 from quicksilver/finderproxytime

Reduce the finder proxy cache time to 0.5s. Fixes #1719