Default attributes not preserved in roundtrip

[tstephen]

Consider this line from reference model A.1.0

  <semantic:task completionQuantity="1" isForCompensation="false" startQuantity="1" name="Task 1" id="_ec59e164-68b4-4f94-98de-ffb1c58a84af">

transformed to this by bpmn.io 0.5.0:

  <semantic:task id="_ec59e164-68b4-4f94-98de-ffb1c58a84af" name="Task 1">

Three attributes have been removed:

1. completionQuantity="1" This is the default (see page 153 / PDF 183) of spec.
2. isForCompensation="false" This is the default (see page 151 / PDF 182) of spec.
3. startQuantity="1" This is the default (see page 151 / PDF 182) of spec.

As noted in each case these are defaults that are removed so no information is lost. However rather than suppressing the finding I propose to flag it as 'Equivalent' since potentially it would pose a problem to the source tool to re-import it.