add a sanity test that ensures the system has a grounding rod (fixes #251)
avoid failing early when the ac, dc, or ground are missing
change all existing tests to only test a single function, even if they're currently failing or incomplete
sanity_9 must detect the absense of a grounding_rod, not the presence of one :P
bah, apparently I was asleep when I wrote sanity_9
Changed some test to not fail.
Changed some case files to not fail.
Merge branch '206-engineering-verification' of ../solarpermit-fork5 into 206-engineering-verification

Conflicts:
	functional-tests/api/case/690_12.xml
	functional-tests/api/case/690_15_D_Pass.xml
tests shouldn't fail if ac/dc/ground are are missing

Added sanity_0 that explicitly fails when the ac, dc or ground nodes
are missing, however.
add pass and fail tests for sanity_8
get sample_system_a.xml passing all the tests

Some of the tests were wrong, some parts of the system were
wrong. nec2014_690_8 is probably still wrong; I think it's conflating
ac and dc current, and trying to compare both with a single max_amps
property.
Merge branch '206-engineering-verification' of github.com:solarpermit/solarpermit into 206-engineering-verification

Conflicts:
	functional-tests/api/case/690_12.xml
	functional-tests/api/case/690_15_D_Pass.xml
Merge branch '206-engineering-verification' of github.com:solarpermit/solarpermit into 206-engineering-verification

Conflicts:
	functional-tests/api/case/690_15_D_Pass.xml
rename a few specifications so that they all follow the same scheme, with the unit at the end
Added 4 new sanity tests.
Merge branch '206-engineering-verification' of github.com:solarpermit/solarpermit into 206-engineering-verification
minor cleanup in the sample system
Added tests for sanity 3, 4, and 5.
Modified case files so that they pass or fail appropriately.
Removed unneeded nodes from tests.