Document the implicit inputs in ModuleInfo's Javadoc

This is hopefully the most logical place.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Support implicit input parameters in modules

It is sometimes important to support parameters that have not been
specified explicitly by the module, e.g. in ImageJ 1.x macros, where we
need to be able to set the macro options as an engine-specific setting
because the SciJava script service runs scripts on threads different
from the caller's and ImageJ 1.x cannot handle that properly without
some handholding.

This change introduces a special class of settings: input map
entries whose key starts with a dot (e.g. .macroOptions) are considered
implicit, i.e.  no errors about "no such parameter" will be produced.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>