Update samplesInContext utility method to handle bare sample IDs

Fix #380.

The new format for the sample filter in context is to just use the
sample ID and not the label and ID in the form {label: label, value:
id}. Because of this, the utility method needs to account for the raw ID
and lookup the label from the sample list as a whole rather than pulling
the label from the context itself.

Signed-off-by: Don Naegely <naegelyd@gmail.com>