Create MIJPrefService

Adds an alternate PrefService implementation to avoid using the
java.util.prefs-based default implementation.

This new service will only be disabled when running MIJ. Outside of MIJ
it should behave as the DefaultPrefService does.

This is necessary to avoid a bug in MATLAB with this package. See:
http://www.mathworks.com/matlabcentral/answers/894-java-usernodeforpackage-function-fails-under-matlab-on-os-x