Adds append_parameter to CompCov; SparseVal bounds

Adds support for append_parameter to ComplexCoverage

Adds bounds to SparseConstantValue - addresses bug with retrieving data bounds from ComplexCoverage
Adds guarding for when domains are None

Adds checks for when the spatial (and temporal) domains are None
Puts base tests under test_complex_coverage

Makes test_complex_coverage inherit from CoverageIntTestBase so it can benefit from the full suite of coverage tests.

Minor fixes to other tests & test classes

Adds get_random_sample to coverage_model.utils - provides a random sample of a given length within the given range
Bump all submodules to latest
Merge pull request #71 from blazetopher/append_param

Append Parameter to coverage post creation