fix the unit for transmissibility when using the metric unit system

I don't know why exactly this happend, but anyway thanks to [at] bska
for catching it...
Merge pull request #383 from andlaus/fix_metric_transmissibility_unit

fix the unit for transmissibility when using the metric unit system
make the build fail if a JSON keyword definition file could not be parsed
Merge pull request #386 from andlaus/abort_build_on_invalid_JSON

make the build fail if a JSON keyword definition file could not be parsed
Added EQUALREG json configuration
Added maskedSet() and initMask() GridProperties<T>
Added const to GridProperty::containsNan()
Added GridProperty::getDimensionString()
Added method GridProperties::getInitializedKeyword()

The getKeyword() method will autocreate and initialize a keyword if you
ask for one which is supported, but has not yet been accessed. The new
getInitializedkeyword() method will raise an exception if the keyword
has not already been initialized.
Added support for EQUALREG in EclipseState
Added test for EQUAL.
Added GridProperty::maskedMultiply() method
Added MULTIREG keyword.
Added support for MULTIREG keyword in EclipseState
Added GridProperty::maskedAdd() and maskedCopy()
Added ADDREG keyword
Added support for ADDREG keyword
Added COPYREG keyword
Added support for COPYREG keyword