Add equality to Path, BeanSetting, Block; don't load duplicate Paths in Block

[bobjacobsen]

This adds equals() and hashCode() to Path, BeanSetting and Block (plus JUnit tests) so code can e.g. check for duplicate/equals Paths in a Block.

No longer load duplicate Paths in into a Block, e.g. if a file is read for a second time.

Related to #677, #678

[kjlisby]

It seems that with this commit, my signal mast logic no longer reacts to block occupancy changes.

That is, if I check out the commit just before this one, my signal masts works fine. But checking out this one or a newer commit, the reaction to block occupancy changes no longer works.

BR
Lisby

[kjlisby]

BTW: As a symptom, I see this null pointer exception from time to time:

2016-02-07 14:22:33,672 ptionhandler.UncaughtExceptionHandler ERROR - Unhandled Exception: java.lang.NullPointerException [B03-B09 B14-B15]
java.lang.NullPointerException
at jmri.implementation.DefaultSignalMastLogic$DestinationMast.checkStateDetails(DefaultSignalMastLogic.java:1948)
at jmri.implementation.DefaultSignalMastLogic$DestinationMast$1.run(DefaultSignalMastLogic.java:1841)
at java.lang.Thread.run(Thread.java:745)