Added Base.showDotNetIntType

Showing the ScriptVal type names is rather less helpful
Added simple test that creates integral variables

The function converts the first argument (a byte list) into a variable
name, and takes an AnyInteget value as its second argument; it then
creates an environment, runs a command declaring a variable by that name
and assigning the correct type, and verifies the results.

Success occurs when the declared variable is found in the finished
environment, and the value in the environment is equal to the value
provided.