add a global context to the Client; issue #40
fix context lookup on the Model
keep context=None except for the interactive mode
preserve the context when re-connecting a client in interactive mode
in interactive mode, copy the context on client.connect(...)
adapt the test case for interactive mode
some cases where the context was lost
simplify getting default context
add changelog entry and documentation for Client.context
add test for 8.0 client
test context in method get()
Merge branch 'global-context'