* Initialise cached option value with options_set's scope so correct
scope is returned.
* Use unordered_map::operator[] as emplace never overwrites.
* Ensure that km_kbp_options_set_to_json() returns the document size
including the null.
* correct scope_name_lut so scope names are in the right order.
While dynamic linking works on linux & Mac OS due to rpath support
Windows can't find the dll when debugging the test case unless it's
copied into the tests builddir or it has it's working dir set to the
DLL's builddir.
