Prepare for 1.0.2
README update
Update jackson dependency
Import RefSanityChecks and related classes from -validator
More class imports from -validator

Namely, loading classes, related exceptions and messages, and
LoadingConfiguration{,Builder}.
Import all loading classes, tests from -validator
Move two tests to their rightful package
Add TODO notes
Add SchemaTreeEquivalence and all of walk/, imported from -validator
Add all tests, classes necessary for examples to operate on walk/

Needs more reorganization, documentation etc.
Add all syntax validation from -validator

With tests.
More imported files
More tests for syntax validation
Javadoc fixes
Add one method to SchemaListener, and make example MutableTree more robust
Parameterize appropriate methods of SchemaWalker and implementations
RecursiveSchemaWalker: prevent infinite loops -- hopefully

The algorithm is rather simple. There is a loop if a reference resolution leads
to the same schema, at a path which is either a parent or a child of where we
came from.

Test this (crudely) by loading the draft v4 core meta schema which is an ideal
test ground for us, since it has plenty of { "$ref": "#" }, which obviously
leads to such a situation.
Make one more method generic
Code nitpick
RecursiveSchemaWalker: make "sibling" test more complete