WCPS - Throw exception for unknown casting type

[Bang Pham Huu]

This WCPS uses unknown casting type byte.

 for c in (INSPIRE_WS_LC)
 return encode( (byte) c, "png" )

and Petascope translates it literally to rasql as

SELECT encode((byte) c, "png") FROM ICGC_DATA_HELSINKI_WS_LC AS c

and it returns error as there is no byte type in rasdaman.

Petascope should throw exception in this case instead.