Made block.base into block.__init__

The "base" module was really serving the purpose of an __init__ module, leaving
the __init__ module free for other purposes. But since the __init__ module was
empty, this didn't really make sense.
Moved salve.execute to salve.action

Also made salve.execute.action into salve.action.__init__, as this has cleaner
semantics than the prior arrangement. The diffset is large for this commit
because there are many imports and mocks that needed to be rewritten to use the
new package location.
Move salve.run to salve.cli & test package renames

Move salve.run to salve.cli (clearer semantics again), and renamed a bunch of
the test packages as per salve.cli and salve.action.
Silence stderr for reader tests

The reader tests were relying on sys.stderr being mocked prior to their runs by
other tests, which is why a rename triggered this error. Problem was solved by
wrapping them in MockedGlobals subclasses.
Moved salve.settings.config to salve.config

Rather than having a whole package devoted to settings, which does not properly
encapsulate the global execution context and other classifiable "settings", the
config package is exposed within the toplevel salve package. This is a clearer
breakdown. Config can be turned into a package if there is a call to do so in
the future.
Merge branch 'refactor/rename-packages' into dev