New Feature: Datasources Expansion and Improved Speed

[PRijnbeek]

Creating a separate issue for this off of the main topic (#217).

Feature 1.

A short description of the feature
Add a new graph in DataSources that shows the number of people that have more than 1,2,3,4 etc occurrences of a concept, e.g. number of BMIs

The organization or developers that are involved in the implementation
EMIF, persons involved: @PRijnbeek, @lhalvors, Michel Van Speybroeck

Any anticipated impact to current WebAPI/Atlas functionality (if applicable)
This has impact on Achilles R, WebApi, (Achilles Web), Atlas

Feature 2.

A short description of the feature
Improve the performance of the datasource tab considerably. Currently, the report loading is very slow because of the on-the-fly creation of the graphs from the Achilles results set. We have improved the speed by adding new intermediate Achilles tables created by Achilles R. This makes the interface responsive again.

The organization or developers that are involved in the implementation
EMIF, persons involved: @PRijnbeek, @lhalvors, Michel Van Speybroeck

Any anticipated impact to current WebAPI/Atlas functionality (if applicable)
This has impact on Achilles R, WebApi, (Achilles Web), Atlas

These features will be combined in one pull request.