Merge Presenting complaint into symtoms

[fredkingham]

We have 2 models that are essentially the same.

https://github.com/openhealthcare/elcid/blob/v0.7.1/elcid/models.py#L149

https://github.com/openhealthcare/elcid/blob/v0.7.1/walkin/models.py#L36

This confuses users when they are extracting the data.

Can we merge these two models.

• [x] Add the onset field and make a migration
• [x] Add a data migration to walkin that depends on the migration in elcid that goes through all of the Symptoms and creates PresentingComplaints. Note we are not deleting the PresentingComplaints at this stage as they contain reversion data. (https://docs.djangoproject.com/en/2.0/topics/migrations/#data-migrations, e.g. https://github.com/openhealthcare/elcid/blob/v0.7.1/elcid/migrations/0051_auto_20170523_0831.py although with different logic in run_python)
• [x] Add a template to https://github.com/openhealthcare/elcid/blob/v0.7.1/walkin/templates/walkin/modals/presenting_complaint.html that uses the term Symptoms rather than presenting complain.
• [x] Change the column in the walkin patient lists to use presenting complaint model but the display name 'Symptoms'
• [x] Change the detail view to use the PresentingComlaint Model but to pass in the title "Symptoms" https://github.com/openhealthcare/elcid/blob/v0.7.1/walkin/templates/detail/walkin.html

[pacharanero]

Should this:

Note we are not deleting the PresentingComplaints at this stage as they contain reversion data.

read '...we are not deleting Symptoms...'

[fredkingham]

We are planning to avoid large db changes to elcid UCH at the moment because development is currently paused. If necessary we will handle these issues in a search rule.