user friendly interface to find_roots!

[kalmarek]

Write find_roots! wrapper in a similar fashion as to how eigvals are wrapped

[Joel-Dahne]

I'll reply to your comment in #125 about wrapping root finding functions here.

No I have not tried to wrap it but have looked a bit at it. I think Fredrik is right in that the implementation in Arb is very simple and it's probably a better idea to implement it directly in Julia. Though there are merits to wrapping the Arb version, making it easier to switch in a reproducible way from a C-implemantation to an Julia implementation is one of them.

If we do decide that it's a good idea to implement a Julia version I'm not sure if Arblib is the correct place to do this. At the moment Arblib is basically a thin wrapper around Arb and I think it's a good idea to keep it like that. Instead one could possibly create another Julia package where we implement methods like these.

In fact I have two such packages for personal use, ArbTools.jl which uses Nemo for the Arb-interface and the newer (but less worked on) ArbExtras.jl which uses Arblib for the Arb-interface. As I said these are mostly for personal use and they contain methods I have needed across different projects, in general they can change quickly and backwards comparability is not prioritized. Some of the methods from these packages, or versions of them, could possibly be put in a public package.