OCSADV-27: Model and parser for VoTable

Model, Parser and tests for VoTable xml. The main public function takes an xml node and returns a list of resources containing sidereal targets. Likely, there will be changes to the model as it is integrated into the AGS and UI

As much as possible the parser tries to retain parsing errors, but at the same will extract as many valid targets as possible
Constructing with `-\/` and `\/-` directly can cause inference issues because the types are too specific (same thing that happens with `Nil` vs `List.empty`) so it's better to use `\/.left` (or `expr.left` if you have the syntax imported) because the resulting type will be `Foo \/ Nothing` which is less specific and will unify with `Nothing \/ Bar` to give you `Foo \/ Bar` where you want it.