s2-geometry-library-java

Target Java 7. Build source jar.

Inline checkEqualsAndHashCodeMethods calls in preparation for deprecating the method.

Per discussion with kirilll, some checks that we desire to run at debug time only have been converted to asserts, and commented out pending an answer from the java libraries team on how best to handle debug time only checks. One of these changes overlaps a change started by ikaushan in CL 25025671 -- hopefully he beats me to the punch.

Removing very slow precondition checks. Removing these yields 10%