Merge pull request
#2211 from minrk/datapub
add data publication message
Functions just like displaypub, but sends a namespace of actual data instead of representations. This uses the serialization/zero-copy machinery of the parallel code.
The current interpretation of a sequence of data publications within a cell is updates of a single namespace. That is, a series of calls to publish_data(dict(A=...)) during a given cell will result in a single dict with the latest value of A, updated in-place. An alternate interpretation could be to keep appending to a list, but I expect the current update approach to be preferable.
Changes along the way:
AsyncResults no longer protect metadata access while results are pending.
This was an artificial limitation, and impedes informed access of incomplete metadata, which actually works just fine.
