- literal lookups only for expression strings
- code reduction for setExprFields.
- changed keyword "condition" to "fieldMask" (option -field-mask).
This is a better description of its purpose and avoids possible
naming ambiguities with functionObject triggers (for example)
if we apply similar syntax elsewhere.
BUG: erroneous check in volumeExpr::parseDriver::isResultType()
- not triggered since this method is not used anywhere
(may remove in future version)
