Introduce namespace adaflo

[mschreter]

In a student project, we use adaflo and the deal.II TimeStepping class (https://www.dealii.org/current/doxygen/deal.II/classTimeStepping_1_1TimeStepping.html). Since adaflo also has a TimeStepping class (see https://github.com/kronbichler/adaflo/blob/master/include/adaflo/time_stepping.h), we get a naming collision. @kronbichler would you agree, if we introduced an adaflo namespace around the whole code? It's a big incompatibility change, but it would help avoid naming collisions in the future.

@j-brotz FYI

[kronbichler]

I would certainly not be opposed to that, because the use of adaflo as a library, which is a typical use case, should make sure to not enter the global namespace. I thus agree with this suggestion. I can look into it next week, or you can provide a suggestion and we see how to proceed from there. I would be happy to help.

[mschreter]

That's good to hear. We are happy to contribute and will prepare a suggestion for it.