add itertrim to getdirbyana

vfatqc-python-scripts depends on gem-plotting-tools, and so these are the changes in gem-plotting tools which are needed to add iterative trimming to run_scans.py in vfatqc-python-scripts

Description

Add iterTrim to list of analysis types in two places.

Types of changes

[ ] Bug fix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)

Motivation and Context

In order for https://github.com/cms-gem-daq-project/vfatqc-python-scripts/pull/275 to work, we need to have iterTrim as one of the scan types known to getdirbyana.

How Has This Been Tested?

Yes, it was tested on the coffin.

Screenshots (if appropriate):

Checklist:

[x] My code follows the code style of this project.
[ ] My change requires a change to the documentation.
[ ] I have updated the documentation accordingly.
[ ] I have added tests to cover my changes.
[ ] All new and existing tests passed.

cms-gem-daq-project / gem-plotting-tools

add itertrim to getdirbyana #248