tmf: Make IOnDemandAnalysis#execute() throw an exception

tmf: Make IOnDemandAnalysis#execute() throw an exception

If execution of an analysis yields an error, it should be reported
to the user. This can be done using a custom exception.

Avoid @Nullable parameters while at it, and document what can be
used instead.

Change-Id: I499ec1938339f6fd6c00e5fb0b5ecf25f082f7ff
Signed-off-by: Alexandre Montplaisir <alexmonthy@efficios.com>
Reviewed-on: https://git.eclipse.org/r/71563
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
Tested-by: Patrick Tasse <patrick.tasse@gmail.com>
Reviewed-by: Hudson CI