Naming is not consistent between submodules

[lexbailey]

there might be some confusion in the naming of the modules and sessions
Specifically these four submodules:

submodule name => session names
----------------------------------
utp-main       => (various sessions, many of which start with 'UTP1')
UTP            => UTP2
UTP-Designs    => UTP-Designs
UTP-Reactive   => UTP-Reactive (already renamed)

Some of the new modules have a 2 in them, others don't.
With the exception of utp-main (which AIUI is just legacy at this point) I think the submodule names and the session names should all align with each other. Currently only UTP-Designs does.

We should either:
1. rename the submodules the include the 2, and rename the UTP-Designs session to UTP2-Designs or...
2. drop all of the 2s (rename the UTP2 session to UTP and the UTP2-Reactive session to UTP-Reactive)

I have no opinion on wether the names should include the "2" or not, but I don't see it being a problem either way.
It is slightly easier from a technical point of view to go for option 2 since it means we don't need to rename the git repositories.
The first option is disruptive to any repo that has any one of the renamed repos as a submodule, and also to users who have cloned the repo under the old name as they will need to update the name to pull the latest changes. The second one is disruptive to users of the renamed sessions who will have to change their theory imports. Either way the disruption is minor, minimal changes are required downstream.

[lexbailey]

Oh, wait, I just saw that the UTP-Reactive session has actually been renamed already. It's now self-consistent, so it's just UTP => UTP2 that's not consistent now (crossed out all the parts of the initial comment that are now irrelevant)