Added check of correct parameter substitution (there shouldn't be ${VAR} in final string)

Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>
Added tests and fixed NPE for the null strings

Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>
Fixed wipeFilter for missing P4CONFIG. Now there won't be "${P4CONFIG}" in exclude directory list

Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>
Merge branch 'parameter-substitution-validation' of git://github.com/synopsys-arc-oss/perforce-plugin into oleg