Suggestions on updating the random-number document

[yaoyi92]

I found it a little bit difficult to use the random number doc. Here are my suggestions:

1. Now, it seems we don't have all the API documented. In the example, it seems to tell if we need an even distributed random double we can call generator.drand(0., 1.). It would be better if all the available APIs for different data types are listed.
2. I am not sure whether random number for other distributions have been implemented. I found double normal in source code. It would be nice to see this been documented as well.
3. Is it possible to document whether the random number can be used in team level or not? My feeling is it won't have any difficulty using it within team policy.

[ajpowelsnl]

Thank you @yaoyi92. Would you like to create a pull request to address the issues you raise?

[ajpowelsnl]

@yaoyi92 - ping