Added a minimal CDC client application that uses the CDC connector
library. This is mainly intended for manual testing so it is built using
the accompanying Makefile instead of being a part of the CMake system.
The recursive calls into `read` caused unnecessary slowness in the
connection phase. The actual first row should only be read when the data
is requested. This can possibly solve the false timeout errors caused by
slow sending of the first row of data.
The iterator to the buffer isn't really needed as the beginning of the
buffer can be used instead. This should make the code more robust. Changed
the internal buffer from a vector to a deque as the latter is more
appropriate for insertion on one end and consumption on the other.
