Metadata diagnosis

[sbesson]

Implement series of changes suggested by @eleanorwilliams.

The most important change are:

• the unification of the Characteristics [Diagnosis] and Experimental Condition [Diagnosis] column - the renaming of Comment [Diagnosis] into Characteristics [Clinical History]
• the integration of the last column into the map annotation

Other minor curation cleanups include the usage of lowercase (not chronic heart failure, heart tissue pathology).

[sbesson]

Awesome thanks @dominikl. Could you add a screenshot here as well so that @eleanorwilliams or others can see how the annotations render?

[dominikl]