Add set-levels! macro

[oubiwann]

This would allow for setting different log levels for different namespaces:

(set-levels!
  'ns1 :debug
  '[ns2 ns3] :info
  '[ns4 n5 n6] :error)

[oubiwann]

There should also be a supporting function for this ... that would make it easier to work with in some circumstances (even if the data structure arg is more complex).

[Kineolyan]

I see this issue was labeled 2 years ago. Is this still an issue that requires work?