- Update open_table for mapistore backend folder prototype to take
  TALLOC_CTX memory context as first parameter

- Add open_table implementation in mapistore_python backend
Add mapistore python implementation for folder.get_child_count
Add mapistore python implementation for table.set_columns
Use hexadecimal version prefixed with 0x rather than decimal value
for unmapped properties.
mapistore_test: Missing brake in a switch
mapistore_test: Load loadparm defaults after setting the debug level

Otherwise it is awasy very chatty during initialization, no matter
what the -d option is
remove unused return value
solve typos in create_folder and add sanity check