Hale Link Objects support improvements

This PR supports the Hale Link Objects extensions as defined in https://github.com/mdsol/hale/blob/misc_modifications/README.md. Still waiting on https://github.com/mdsol/hale/pull/2 being merged.

Supported:
```
4. Link Objects
 4.1. method
 4.3. render
 4.4. enctype
 4.5. target
```

4.2 Data is coming soon as its big enough to deserve it's own PR.

@mdsol/hypermedia-team Please review and merge.