[EPIC] Base for the next release 1.6.0

[ethouris]

The list of PRs merged to dev-1.6.0 branch.

Note that those already merged to master have been removed.

• [FIX] Calculate correctly max payload size per UDP packet #2677 (conflicts resolved)
• [BUG] Fixed the use of the right error constant #2595
• [core] Fixed bug: srt_accept failure may make accepted socket leak #1884
• Added messages for access control rejection messages #2606
• Implementation of SWIG with C# bindings #2577
• [BUG] Removed setting +W for a listener socket after accept ready #2732
  • small collision with [BUG] Fixed the use of the right error constant #2595

NOTE: PR #2710 is created for CI only for the dev-1.6.0 branch.

[ethouris]

Replaced by #3141