Add support for Conan dependency manager

[samhatchett]

Conan is a widely used C/C++ package manager. It allows calling projects to pull in deps based on a repo url, and will automatically build epanet as a part of a larger project.

The addition would be a single python file at the top level that specifies some basic build configuration info. I have an example ready to go into a PR if interested.

https://conan.io/

[LRossman]

I have no objections - go for it.

[Mariosmsk]

looks good addition!