Use symbols instead of strings for option names

[maxitg]

The problem

We currently prefer using strings over symbols for options. This, however, is not consistent with conventions even for new System`* symbols in Wolfram Language. As a result, some of our options (ones identical to existing System` ones) use symbols and some use strings. Users are then required to remember which one is which.

Possible solution

I suggest to switch to using symbols for option names. This will require writing usage message for each of them and making sure they don't conflict with system symbols and other packages.