Added API.split

Helper function for String.Split()
Added API.LoadAssembly and API.loadAType
Added API.doRootNamespace
Corrected typeNamespaces = [] case in API.doRootNamespace
Added return type spec to API.doRootNamespace
Added empty API.doRootType, filled in doRootNamespace

Now calls to doRootType to update or create the children for a
namespace.
Changed Base.Env to use System.Reflection.Assembly for external libs

By using the external libraries as Assembly objects rather than as the
API.Namespace objects, there's no longer a need to parse out a tree of
namespaces and type definitions, as Assembly.GetType(string) can be
used.

At the moment this means that the scripting environment will not have
support for types defined within other types. This is due to the way
that sub-types are defined with reflection as Namespace.Parent+SubType
rather than just Namespace.Parent.SubType as written in the .NET
languages that I'm aware of.

This pitfall could be addressed at a later date by attempting to replace
the periods with plus-signs while repeatedly calling to
Assembly.GetType().
Added parser support for "Dim x As New Namespace.Type(value)"

Comes out as:

List[
    Atom "declare";
    Atom "x";
    List[
        Atom "dot notation";
        Atom "Namespace"
        List[
            Atom "method call"
            Atom "Type"
            List[
                Atom "value"
                ]
            ]
        ]
    ]

Hope reading that was as fun for you as it was for me!
Sorry, back to third-person.
Corrected parsing "Dim x As Namespace.Type"

Builds as:

List[
    Atom "declare"
    Atom "x"
    List[
        Atom "dot notation"
        Atom "Namespace"
        Atom "Type"
        ]
    ]
Added support for "Dim x As Namespace.Type = New Namespace.Type(value)"

Builds as:

List[
    Atom "declare"
    Atom "x"
    List[
        Atom "dot notation"
        Atom "Namespace"
        Atom "Type"
        ]
    List[
        Atom "dot notation"
        Atom "Namespace"
        List[
            Atom "method call"
            Atom "Type"
            List[
                Atom "value"
                ]
            ]
        ]
    ]