Make edit_[:document_type] method more generic

Editing a document is requires nothing different for each document format. It simply fills in fields, saves and publishes them. By moving the step to go to a particular page we can make this method much simpler. This will allow us to have more generic methods accross the board removing a massive amount of duplication and making the cucumber steps much easier to work with.
Allow CmaCases to be edited with change notes

As with Manuals CmaCases can now be edited with change notes.
Currently these change notes will only be stored against the
SpecialistDocumentEdition and do not create a PublicationLog entry.
 Which currently means change notes will not be able to be used on
the frontend yet. This would require some work in order to make the
PublicationLog work with other formats other than manuals.
Rename dsu_fields to document_fields

This makes it much easier for us to use common steps accross the document formats.
Allow DrugSafetyUpdates to be edited with change notes

As with CmaCases allow change notes which are not yet pushed to the PublicationLog
Rename maib_report_fields to document_fields
Allow MAIB reports to be edited with change notes

As with CmaCases allow change notes which are not yet pushed to the PublicationLog
This is a duplicate step to that in publishing maib
Rename @msa_fields to @document_fields for reusability
MedicalSafetyAlerts can be edited with change notes

As with CmaCases allow change notes which are not yet pushed to the PublicationLog
Rename msa feature to use correct spelling
Rename @raib_report_fields to @document_fields
RAIB Reports can be saved with change notes
Remove duplicate of a publishing spec
Use @document_fields over @aaib_fields
Make AAIB Reports use change notes
Use @document_fields over @idf_fields
Add change notes to International Development Funds