Realigns API for View and Complex coverages

Minor realignment of API's for ViewCoverage and ComplexCoverage

Renames ComplexCoverageType.PARAMETRIC --> ComplexCoverageType.PARAMETRIC_STRICT to accomodate the forthcoming (hopefully) ComplexCoverageType.PARAMETRIC_LOOSE
Fixes bug with persistence of 'coverage_type'
Adds ViewCoverage.replace_reference_coverage; tests

ViewCoverage.replace_reference_coverage allows 'replacement' of the underlying reference coverage of a ViewCoverage

Testing for replace_reference_coverage and head_coverage_path
Adds testing for ComplexCoverage.head_coverage_path

Downgrades some logging (warn -> info and info -> debug) and some minor cleanup
Merge pull request #64 from blazetopher/view_cov

View Coverage