Tidy up

[e-kwsm]

#2088

[ghutchis]

Why? For many reasons, we removed the math checks because they're very slow.

[e-kwsm]

For 6af03f1, an input is not always normalizable and exception is thrown (#2088).

For 80468c4, the default release type is Release and NDEBUG is defined (e.g. L444), therefore performance is not harmed.
For vector3::operator[], probably switch with default would be better.

[e-kwsm]

switch is used; I hope performance is not worsen.

[ghutchis]

I've had this debate before - if there's a crash, the problem is in the calling code (e.g., GetNewBondVector in your linked example).

This code is called a lot in tight loops. Many builds are RelWithDebInfo which would still enable your checks.

[e-kwsm]

Change about NDEBUG is reverted.