Enable lowercase in CREATE_TIMESERIES sql

Now in createTimeseries sql, datatype and encoding value must be uppercase.

For example, "create timeseries root.vehicle.d1.s1 with datatype=INT32, encoding=RLE".

"create timeseries root.vehicle.d1.s1 with datatype=int32, encoding=rle" is not allowed.

For convenience, the lowercase format input should be allowed.