Break up the swift pollsters

This change also adds a test dependency on testscenarios,
a library for reusing test class definitions for parameterized
tests.

blueprint one-meter-per-plugin

Change-Id: I0e1e0e4e225261598cc28d2e3335be6f163bbc85
Signed-off-by: Doug Hellmann <doug.hellmann@dreamhost.com>
Merge "Break up the swift pollsters"