Fix compaction_filter.h typos
C API: Add support for compaction filter factories (v1)
C API: Allow setting compaction filter factory
C API: Add test for compaction filter factories

Also refactored the compaction filter tests to share some code and ensure that
options were getting reset so future test results aren't confused.
Merge pull request #191 from edsrzf/c-api-compaction-filter-factory

C API: Add support for compaction filter factories (v1)