Usability: Rename the yang.data.api.InstanceIdentifier to yang.data.api.YangInstanceIdentifier

One of the comments on usability of MD-SAL is that classes with the same name make it really difficult to use and interact with MD-SAL.

On that front, we would like to rename the InstanceIdentifier class name, for which there are two classes (a binding aware and binding independent version).

org.opendaylight.yangtools.yang.data.api.InstanceIdentifier to org.opendaylight.yangtools.yang.data.api.BIInstanceIdentifier

and

org.opendaylight.yangtools.yang.binding.InstanceIdentifier to
org.opendaylight.yangtools.yang.binding.BAInstanceIdentifier

By renaming these classes we can make it clearer if we are using the BI or BA version, and it will also allow them to coexist in the same class with out having to fully qualify the class names.