Revert "removed "getest" since it is duplication with autotest (and we use mainly the later for regression testing)"

This reverts commit b6464cf5e7dbbd82322de59a3c1f87b9bfd2913a.
getest: all test cases now passes again

This commit also introduces a new JSON converter for UC_STRING:
JSON_UC_STRING_CONVERTER. This converter is especially used in the JSON
DS_HASH_TABLE converter to retrieve UC_STRING instances instead of STRING_32.

Some more ecf files now use Gobo FreeELKS version when GOBO_EIFFEL is ge.

Note that we can't run the tests using gec for now as the ecf used for Gobo
(which are shipped with EiffelStudio) don't use the Gobo FreeELKS version
(they use the ISE version)