Add a new program, loadtest, that runs a requested number of client sessions
in parallel to a loolwsd server. A client session loads one of a list of test
documents, and does some operations on it.
Move the getTokenInteger() and getTokenString() functions out from LOOLSession
into a new namespace LOOLProtocol, as they are neeeded also in the loadtest
program.
Add, also in LOOLProtocol, functions to parse some of the messages from the
server. (In general that is done in client JavaScript code, of course; only
for testing purposes needed in C++ code.)
Handle the start of a child process when needed centrally, not in each command
handler.
Also, handle unrecognized commands always already in the parent
process. (Command syntax checks still done in child process, though.)
For now, each LOOL client has a separate child process (or none at all, if it
has accessed only information found in the cache). This will obviously have to
chnage to handle collaboration. Etc.
The parent process talks the same Websocket protocol with the child
processes. When there is a child process for a client, traffic from the client
is forwarded as such to the child process and vice versa.
Having a 'close' would mean being able to do a new 'open', too, which
introduces unneeded complexity, at least at this stage.
Just start a fresh WebSocket connection for each document.
