Data Acqusition: add support for multiple diseases in HealthMap alerts. This results in one DiseaseOccurrence per disease, associated with the same alert.
Support HealthMap's "comment" field that contains sub-diseases such as "pf" for Plasmodium falciparum. Store these in a new sub_name field of the healthmap_disease table, so uniqueness is now across name and sub_name.
Make splitComment return a set to remove duplicates
Restructure the HealthMap subdisease handling code given that subdisease names are globally unique (not just unique per disease).
About text typo
Add HealthMap reviewed date to the Alert table, and use it by default in the web service parameters.
HealthMap data acquisition now ignores alerts whose place_category field contains one of the configured "place categories to ignore" (e.g. "imported case")
Merge branch 'master' into healthmap-changes
Merge branch 'master' into healthmap-changes
Add missing foreign key
Fixes following review
Merge branch 'master' into healthmap-changes

Conflicts:
	src/PublicSite/web/WEB-INF/freemarker/about.ftl
Merge pull request #323 from SEEG-Oxford/healthmap-changes

Changes for HealthMap