Dividing Iteration Classes

[talbring]

Proposed Changes

This divides the iteration files and adds a factory class for their creation. A rework of the iteration class is still necessary, but I don't have time to do that at the moment.

Related Work

Resolve any issues (bug fix or feature request), note any related PRs, or mention interactions with the work of others, if any.

PR Checklist

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• I am submitting my contribution to the develop branch.
• My contribution generates no new compiler warnings (try with the '-Wall -Wextra -Wno-unused-parameter -Wno-empty-body' compiler flags).
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• [] I have added a test case that demonstrates my contribution, if necessary.
• [] I have updated appropriate documentation (Tutorials, Docs Page, config_template.cpp) , if necessary.

[pcarruscag]

I wonder if we need documentation strings on the derived classes, especially on this class family this stuff is out of date all the time.