Add ability to track drug regimen

[Mark Tully]

Add the ability to record the different medications the user is using and also track the times of taking these medications.

A separate tab should be created to list the medications the user wants to record, along with the ability to add and remove medications to this list. The 'Add a reading' dialog should be expanded to include the ability to add the taking of a medication. The graph should show when medication was taken (by a vertical line similar to the current Average Glucose Level line). Different types of medication (eg. tablets, different types of insulin etc) should be shown in different colours.