rename test because it really is going to be a small unit test
refs #18
implement a few initial checks
refs #18
adding actually_skipped parameter because we will want it in splitVector
refs #18
NULL -> nullptr, I'm rusty from mongo work
refs #18
fix some old apis to fit what get_key_after_bytes needs:

make keyrange_compare_s hold an FT instead of FT_HANDLE to prepare for reuse refs #18

make keyrange_compare_s hold a const dbt refs #18

fix const-correctness of fill_bfe functions refs #18
add unit test for an empty dictionary
refs #18
implement get_key_after_bytes for a single basement node, passes simple tests
refs #18