Replace extensions with standard resources

[michaelonken]

[via data4life]

• DDG DMP Enrollment Reason extension: Could be Condition resource
• DDG DMP Relevant Events extension: Could be Condition resource
• DDG DMP Emergency Inpatient Treatment Events extension: Could be Observation resource
• DDG DMP Severe Hypoglycemia Events: Could be Observation resource
• DDG DMP Opthalmic Retinal Examination: Could be Procedure resource (or Observation?)

[michaelonken]

Closed via b7324d3370e79c5e0739e2b481b31f42b9b2f5ca