Plus42 Equations, Preview Release

[Thomas Okken]

New update:

1. Changed one-dimensional array/list indexing back from 0-based to 1-based, for compatibility.
2. When doing the nice new error reporting for generated code, also return back to normal user code, so the user isn't left looking at uneditable code needlessly.
3. In the equation editor, prevent STO from writing code into generated code.