Add UnableToLoadDeckInput Exception
Move input checking out of checkOptions

Relocates input checking as late as possible so that inputs
to NetTest can be downloaded after instancing a NetTestLoader.
Adds class TestDeck

Provides a container for NetTests and helper functionality to
download and verify input arguments if specified by URL.
Make oonicli download inputs before starting tests.
Remove inlineCallbacks
Use default collector from config file
import defer
Catch ProbeIPUnknown and exit
Allow for user-supplied inputs in data/inputs
Don't remove a failed reporter twice