MOTECH-949 Pill Reminder Module topic

Ports documentation from old wiki to Sphinx, with small updates
(removed unsupported mentions about adherence, added outline of
OSGi service API, brief comment about events exposed as tasks).

Change-Id: Ic3e433ad9eb1a46c0f7b9021882396fe16696152
Merge "MOTECH-949 Pill Reminder Module topic"