Power and root symbols should be renamed to avoid confusion

[gkronber]

The symbols are interpreted as

• power(x,y) = power(x, round(y))
• root(x,y) = power(x, 1.0 / round(y))

Consequently, the symbols are also not supported by the AutoDiff converter and the simplifier also assumes these semantics.

Instead, the interpreter should also support power and root without rounding (producing NaN values) and the symbols which lead to protected evaluation (with rounding) should be renamed accordingly.

Suggestions: ProtectedPower, ProtectedRoot or IntegerPower, IntegerRoot.