reworking and adjusting the output table function

[Dr3ven]

I want to improve the output tables functions.
E.g. the old output tables function uses a dict inside a function to find the parameter description/name from the corresponding variable. I want to try to improve this to be more independent of the hard coded dict and descriptions.

Additionally, the tables are adjusted for the new rheologies that were added with #99.

[albert-de-montserrat]

It would be nice to improve Tables.jl indeed. Taking a quick look, some suggestions:

1. Get rid of all the global variables.
2. There is a lot of code repetition in Phase2Dict. You can avoid all that type-based branching by defining small functions and using multiple dispatch.
3. In general, all the functions are quite large and monolithic. Splitting them into smaller functions is probably a good idea when possible. Code will probably more clear and may also lead to code re-usability.

[albert-de-montserrat]

Are you still planning to work on this? I am wondering whether it would makes sense to move this out to an external package, something like GeoParamsTables.jl, so we can move out some dependencies that are not really needed when one uses GeoParams in a solver or similar.

[Dr3ven]

Are you still planning to work on this? I am wondering whether it would makes sense to move this out to an external package, something like GeoParamsTables.jl, so we can move out some dependencies that are not really needed when one uses GeoParams in a solver or similar.

I do not have a lot of time at the moment, but I will finish this pull request once I have more time again.
Concerning the tables feature, the only output dependency that I use is Unidecode.jl as far as I know. So, I don't mind moving the tables to another package if that helps. I guess I would need to rethink how to code some stuff then, but just do as you think suits best for GeoParams.

[albert-de-montserrat]

I think it make sense to move it out. It is not really needed inside GP. And I don't think it will change the current code structure, since its already a submodule, just need to update a few lines of code here and there.

[boriskaus]

I'm fine with moving this to a separate package