Programmatic UX Improvements

A lot of these changes simply make it easier to use this library (and the data) in Python (and other systems). However notably, this PR is shipping with a new database change that isn't required but is recommended. See the "running-extra-scripts.md" file in the admin-docs/ directory after updating your deployment repository with the latest changes from cookiecutter.

What's Changed

• feature/truncate-sentences-in-transcript-str by @isaacna in #153
• bug/catch-timeout-in-event-gather by @isaacna in #157
• feature/store-session-content-hash-in-session-db-model by @isaacna in #158
• feature/script-for-retroactive-session-content-hashing by @isaacna in #159
• feature/role-title-constants by @dphoria in #155
• feature/remove-is-required-from-constant-validator by @isaacna in #163

Full Changelog: v3.0.3...v3.0.4