Improvements to SCL compiler error messages

Better error message if type annotation has different number of
parameters than the function definition.

Refactored method names, we have now getSyntacticFunctionArity for
estimating function arity without type information and
getFunctionDefinitionPatternArity for arity calculations of patterns.

refs #6897

Change-Id: I032ee0e5da416f232517d1e03c7a7cb0208c4d45