Fix the correct return formats for frame endpoints

[emelalkim]

We need to define the correct return formats for WADO-RS and WADO-URI endpoints for frames and fix them.
Should we use similar format to #63?

WADO Path	Return format
WADO-RS frame	multipart/related
WADO-URI frame	application/dicom (DICOM Part 10)

Are we going to support/respect accept header sent from the client? which types we need to support?
I created this issue to start a discussion to define the best solution. We appreciate any input @pieper, @swederik, @hackermd, @lassoan

[pieper]

I started a spreadsheet to track this here: https://docs.google.com/spreadsheets/d/1TE_l96klwEJ3kDqql3usE7sfd9f1v6l197UWF8Vt8YA/edit#gid=0

Please anyone add comments to flesh out all the cases