Map OMOP data to `inpatient_episodes` table

[razekmh]

Extract data from the example OMOP data to fill the inpatient_episodes table from the validate article. This is a split from https://github.com/SAFEHR-data/ramses-package/issues/17

Please feel free to assign yourself to the issue. Please the respective branch for development.

[AngharadGreen]

• For this issue I have used the updated OMOK v0.3.0 to generate OMOP mockVisitOccurrence and mockProcedureOccurrence tables as these tables can be mapped to the RAMSES inpatient_episodes table.
• For the RAMSES inpatient_episodes table the variables admission_method, last_episode_in_encounter, consultant_code and main_specialty_code are difficult to map to the OMOP CDM - I am looking into this in more detail to determine what OMOP tables would be appropriate to map to, as these variables must not contain missing data.