HTTP Servlet binding acceptance should be tested before the availability of the path

[tcalmant]

When two servlets services are to be bound on a same path but on two different HTTP services, the bound_to() method is not sufficient to have a clean behaviour: an exception will be raised when the second servlet path will be tested.

The solution could be: 1/ let the servlet register itself in the bound_to() method, if it accepts the server description 2/ let the servlet implement a new method (e.g. accept_server()), called before the servlet path check.

[tcalmant]

Done in commit 44f68020e843d62c8dcbb02673913ade15c00ab8. Servlet might have an "accept_binding(path, parameters)" method:

• if it returns False, the registration, is aborted
• else, the path availability check is then done, raising a ValueError or then calling the bound_to(path, parameters) method.