Change all scripts and files to use assertion description in assertions.csv

Currently, the description for an assertion found in any csv output can come from a multitude of places. However, assertion.csv that is copied from the TD spec is the only place that should have this. Thus, we should change our tooling to use only that. This means:
- Removing description from assertion schemas
- Removing it from csv files inside assertion-td and tm
- Scripts that do some checks
- Manually checking where else it can be inserted

Once that is done, anytime we need to output a csv file, the assertion description should be copied from assertions.csv

@FadySalama do you see potential problems?