XD-2230 Fixed script module options and ability to specify inline variables

properties-location -> propertiesLocation and functionality restored. 
Affects processor:transform, processor:filter, processor:script, sink:router.

With --script we now have the ability to bind variables in line, e.g., --variables='foo=FOO,bar=BAR' which is a lot cleaner than an external properties file unless there are a long list of bind variables. These options may be combined with --variables replacing any values duplicated in the propertiesLocation. 

Documentation for affected modules will be updated accordingly. 
The metadata/mixin classes can't return non-String parseable results (at least at the moment), as those are later injected as Strings in the placeholders. If we really can't use `null`, then I'm totally fine with the fake location (rather than a complicated profile)