Consolidate options, prefs and config logic

Currently, we have a package `org.scijava.options` with an `OptionsService`, as well as a separate `net.imagej.config` package with a `ConfigFileParameters` class for working with the ImageJ.cfg launcher file. We also have `org.scijava.util.Prefs` for managing persistence of key/value string pairs.

We should strongly consider consolidation of all these, eliminating any redundant concepts.

Migrated-From: http://trac.imagej.net/ticket/1451

Start by reading org.scijava.options.OptionsService, net.imagej.config.ConfigFileParameters, and org.scijava.util.Prefs to map their responsibilities and overlapping concepts. Compare how each handles configuration or persistence, then define a consolidation plan and verify that the existing launcher-file and key/value preference use cases remain covered.

Written by the indexing model from the issue text.