performance checks

[skeating]

Performance metrics that we need to watch:

• How much CPU time does the waveform HL7 reader take to parse HL7 and generate interchange messages?
• Can core proc process waveform messages quicker than the rate at which they're being produced, on top of the messages it's already processing? (live mode)
• How much does this slow down a validation run? (catchup mode)
• How much storage space does this take in the postgres DB?
• Can we run the read queries we need to do in a reasonable time?

[jeremyestein]

Closing because these are requirements not tasks. For design discussion see https://github.com/UCLH-DHCT/emap/blob/jeremy/hf-data/docs/dev/features/waveform_hf_data.md