Plot every data point on graphs

[adamdewey]

Is your feature request related to a problem? Please describe.
The graphs are improved since #259 but can still be misleading due to averaging.

They would be more accurate if each data point could be plotted individually (e.g. would allow user to identify temperature spike accurately).

Describe the solution you'd like
Every data point to be plotted.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
There's a possibility the tablets may freeze if a large date range is selected, but think this is relatively unlikely - more likely for user to just use the default 24 hours.

Hopefully an app restart should fix a frozen tablet.

[mark-prins]

perhaps display max / min points within the averaged range a la oms
worth testing the performance of an 'all points' solution too