Added basic type class instances for Quaternion.
Added basic type class instances for Quaternion.

There are a few FIXMEs in there, some of which will be more challenging
than others to actually "fix".

Also, fixed a but in nroot.

non/spire,rklaehn/spire,JackSullivan/spire,adampingel/spire,siddhartha-gadgil/spire,tixxit/spire,codeaudit/spire,AlecZorab/spire,kevinmeredith/spire,JackSullivan/spire,kevinmeredith/spire,adampingel/spire,siddhartha-gadgil/spire,tixxit/spire,woparry/spire,guersam/spire,non/spire,codeaudit/spire,rklaehn/spire,woparry/spire,AlecZorab/spire,guersam/spire