Add promiscuous mode for ServerAssociation

[nickamzol]

This PR introduces a new promiscuous flag field for ServerAssociationOptions to allow unknown abstract syntaxes.

Fixes #477

[Enet4]

Thank you for looking into this @nickamzol! Could you write a test with this PR? You can see some examples of client/server DICOM interactions in directory ul/tests, it should be mostly a matter of creating a new test file with a similar DICOM association scenario with presentation context negotiation where the association acceptor is set in promiscuous mode.

[nickamzol]

As requested, I've added both a positive and a negative test case for the new promiscuous mode.

In the positive test case, a server association with promiscuous mode enabled is established. The client requests MR Image Storage, which is not explicitly defined in the server association options as an accepted SOP class. The SCP will accept this as it is set to promiscuous mode.

In the negative test case, a server association with promiscuous mode disabled and Ultrasound Image Storage as an acceptable SOP class is established. The client requests MR Image Storage again, but this is expected to fail, because the SCP does not explicitly accept this SOP class and it's not set to promiscuous mode.

[luckfamousa]

Great @nickamzol that is exactly what we need!

[Enet4]

The code looks spot on, and it's well tested! 👍

I will take care of expanding this capability to dicom-storescp. Thank you!