make logging explicit and fix a function

[sunayana]

• makes RICHDEM_LOGGING flag explicit in CMakeLists.txt
• fixes assert in FM_OCallaghan template function.

[r-barnes]

The assertion doesn't look it needed fixing. I've incorporated the cmake change. I wasn't able to take the PR directly because of the blast radius on the whitespace.

[r-barnes]

My bad. I've fixed the assertion in FM_OCallaghan now - thanks!

[sunayana]

Thanks @r-barnes. Also to let you know we used richdem in Cervest and created a Julia wrapper for your code, here is a link to the fork:
https://github.com/Cervest/richdem
and the Julia wrapper is here:
https://github.com/Cervest/richdem/tree/master/wrappers/RichDEM.jl

[r-barnes]

@sunayana - Cool! Would you be interested in trying to merge that all upstream? I can get you some collaborator access to the repo if that's helpful.

[sunayana]

@r-barnes - Yes I would be happy to push the changes upstream if you would give me collaborator access to the repo. Thanks!