[RFC][PATCH 13/22] JavaHL Ra API Implementation

[[[
    JavaHL: Factor out common progress and cancellation callbacks as well
as configuration and authentication context into CommonContext class from
SVNClient specific code in the ClientContext class so that it can be shared
with the Ra JNI code

    [ in subversion/bindings/javahl/native ]

    * CommonContext.cpp, CommonContext.h, ClientContext.cpp, ClientContext.h
      (username, password, getConfigDirectory, setConfigDirectory,
setPrompt, cancelOperation, progress,): Move from ClientContext to
CommonContext

    * CommonContext.cpp, CommonContext.h
      (attachJavaObject): Create new function to hold common logic of
attaching to the java CommonContext class used for callbacks
      (getConfigData, getAuthBaton): Split getContext into separate
configuration data setup and authentication data setup to better reflect
their different life cycles
      (getClientName): New function to return client name that should be
used in callbacks

    * ClientContext.cpp, ClientContext.h
      (ClientContext, getContext): Use the factored out CommonContext
member variables and functions
]]]