Obex library cleanup, second pass.

o Use mMemberField variable naming as per style guide
o ClientSession.trans is only used in the ctor, doesn't need to be a member
o Rename connectionOpen to mOpen and isConnected to mObexConnected to reduce
  confusion
o Refactor duplicated code into helper functions (setRequestActive())
o Fix whitespace around comment blocks
o Change unnecessary public scope's to package private (eg setRequestInactive())
o Remove a redundant factory method ClientSession.createHeaderSet()
o Rename OPTIMIZATION to TODO to match Android style
o Rename java.io.IOException to IOException
o Be consistent with variable naming - use header not headers