Topological vector spaces

[mkerjean]

Motivation for this change

Adding the theory of topological vector spaces

Checklist

• added corresponding entries in CHANGELOG_UNRELEASED.md

• added corresponding documentation in the headers

Reference: How to document

Reminder to reviewers

• Read this Checklist
• Put a milestone if possible
• Check labels

[mkerjean]

If I understand correctly, the evt2 branch still depends on the old hierarchy builder branch and not on the master branch which is now ported to hierarchy builder, hence the MC2 label.

[mkerjean]

For the record, a previous comment on PR#539, now closed by @zstone1 "With a long-term goal of doing spectral theory, I'm looking at defining integrals for a TVS. The most straightforward choice seems to be "weak integrals"."

[affeldt-aist]

The last commit makes the dev compile but it is clearly a temporary fix.