Include heart rate (pulse) information in BP measurement view

[asorici]

Why

For a medical professional, the heart rate is very important TOGETHER with the systolic and diastolic values ... because of many things - including that a higher heart rate will (although not linearly) produce an overly high blood pressure. Thus, if the heart rate is higher than usual, the blood pressure might not be relevant to look at ... and thus, we need to see the sys, dia and pulse together

What

• include another bar, along with systolic and diastolic ones for heart_rate (since values are in the same ballpark, the graph should normally not get skewed)
• if the graph becomes too dense, display history for last 5 days, instead of 7
• to identify pulse readings that come from a BP measurement, use the device and timestamp fields in the JSON to do the filtering (they must have the same value as for a BP measurement)