-added UNDEFINED cases in data type enums to avoid unpredictable behaviour.
-Many switch statements did not handle default, fixed that
-added enums to is_empty check of SGParamInfo
-to_string method now doesnt throw an error when data types are undefined
same as before
Merge pull request #1631 from karlnapf/develop

added undefined cases for data type enums
WIP: adding complex64_t <-> numpy complex mapping (issue #1493)