Support subtree filtering in logic and html datapath formats

[amorenoz]

When tree view (HTML or Console) is filtered, we're currently filtering individual flows beforehand which leads to:

• Missing valid flows (if the parent flow is filtered out)
• Having incomplete trees

With this PR, we first build all the subtrees and then filter out those where NONE of the subelements match the filter.

Signed-off-by: Adrian Moreno amorenoz@redhat.com