Move samp to PyVO package #9763

Description

At Astropy Coordination Meeting 2019, it was decided that this should happen. When the move is done, we also need to move the relevant open issues over to PyVO or close them.

Additional context

xref astropy/pyvo#155 (comment)

p.s. A bingo winning issue!

TODO

• Open a PR at PyVO. See Move astropy.samp to pyvo.astropy_samp pyvo#729
• Once PyVO accepted PR, discuss their release timeline.
• Once PyVO release timeline is know, discuss deprecation period of astropy.samp.
• Implement deprecation. Would be nice to get this in for 4.3 8.0.
• Open issue to completely remove astropy.samp after a deprecation period. Would be nice to have that happen for 5.0.
• Make announcements.