Upgrade units-in-java filer parser to handle GNU Units's current file syntax

[buttercookie42]

GNU Units can now set arbitrary variables during parsing (either set externally, or a default value read from the units file) and then skip lines not just based on locale, but also those additional arbitrary variables.

This would be a step (hopefully maybe even the only step required) towards using a current unit definition file from GNU Units.

It seems the syntax for specifying functions also changes slightly, with a few more optional parameters, instead of only the function's dimensions.

And with plain unit definitions a preceding "+" suppresses the redefinition warning.

See https://www.gnu.org/software/units/manual/units.html#Database-Syntax