[Persistence_matrix] Type renaming to be more coherent with Gudhi conventions

[hschreiber]

All types are now starting with a capital letter, with no "_type" or other at the end, as discussed in #917:

          So, if I understood well, your preference would be: all types start with a capitalized letter and only the name of object without any "_type" or "_t" at the end? Eg. `dimension_type` ---> `Dimension`.

Originally posted by @hschreiber in #917 (comment)

          Yes on the description of my preference, I think that's mostly what we've been doing so far in Gudhi (with obvious exceptions like value_type for compatibility with the standard library, or Thing_type where "type" is not in the C++ sense but means "kind", "category").

Originally posted by @mglisse in #917 (comment)

[mglisse]

I didn't check all of them in details, but it looks good to me.
A couple oddities:

• Boundary_container is a container to describe the content of 1 boundary, while Column_container is a container that contains many columns?
• Column::Column::iterator (we already had that before this PR)

[hschreiber]

I didn't check all of them in details, but it looks good to me. A couple oddities:

* Boundary_container is a container to describe the content of 1 boundary, while Column_container is a container that contains many columns?

* Column::Column::iterator (we already had that before this PR)

Now that you are saying it, it looks indeed odd. I changed Boundary_container to Boundary_range and the inner Column to Column_support. Is it better?

[VincentRouvreau]

I did not review them all, but this is the exact role of these code conventions (characteristic_type becomes Characteristic, the syntax says it is a type, and it is clearer)