WCPS - Supporting .re/.img for complex number

[Bang Pham Huu]

For Sentinel 1 SLC which is complex data, WCPS needs to support .re and .img as same as in rasql to select the real and imagine parts.

Currently, it will throw exception as it thinks they are the non-existing bands of the coverage.

for c in (S1_SLC_IW_VV) return encode(c.re, "csv")

with error

Offending token is 're'. Reason: mismatched input 're' expecting {REAL_NUMBER_CONSTANT, COVERAGE_VARIABLE_NAME}.