Fix Intellisense menu for Error

[jmagaram]

This removes all the submodules like SyntaxError and RangeError that had a single function in it - make - and moves these to the top level like makeRangeError and makeSyntaxError. This is more like the old Js.Exn module and makes the Intelliense menu a lot easier to navigate. You can quickly see the types of errors you can create. It is still a 2 step process - make then raise - even though in 99% of the cases the user will throw immediately; this is a step backward from the Js.Exn module that has raiseSyntaxError and other variants.

Before:

After: