[CCUT] support detecting plural form of units

[basels]

When find_best_unit_match(..) is evoked we would like to check the singular form of the unit before returning a NULL type
For example: meters
Instead of getting:

UNKNOWN DIMENSION
UNKNOWN TYPE

We would like to get:

L
http://data.nasa.gov/qudt/owl/unit#Meter

Originated in this issue.