Finally make derived model-object Link consistent with the previous
few commits that tried to do away with the WKT element, as it is
redundant to the shape field.

Changes to be committed:
modified:   src/main/java/edu/berkeley/path/model_objects/network/Link.java
modified:   src/test/java/edu/berkeley/path/model_objects/network/NetworkTest.java
Merge pull request #167 from tmkpath/dev

Finally make derived model-object Link consistent with the previous