Spring Allow to customize separator for messaging destinations

In order to be able to use separators like "." (used by default by most broker relays) instead of "/" for destination patterns handling, the PathMatcher used in spring-messaging can now be customized easily thanks to XML websocket namespace or JavaConfig.

AntPathMatcher has been updated in order to use the configured path separator instead of an hardcoded "/" for path concatenation. Extension handling is now disabled when the "." separator is configured.

Issue: SPR-11660

Comment From: sdeleuze

@rstoyanchev Could you have a look to this PR and send me your feedbacks please ?