Monitor resources can now be altered with a PUT request. The method allows
alterations on all parameters that the maxadmin `alter monitor` command
allows.
The server can now be modified with a PUT request of a modified server
resource. The server resource was reorganized to have the parameters as a
separate entity from the other more general entities of the resource.
The PUT/POST functions return a more appropriate error message when no
request body is provided.
Moved some of the constant names used in server.cc into the config.h
header.
