Added support for multi-router registration

Added support for multi-router registration
replaced unnecessary <domains><domain/></domains> with a single <domain> element in opensrf_core.xml
wrapped the top-level <router> element in a <routers> container element in opensrf_core.xml to
    support additional router configuration
Updated the python, C, and Perl to match the above changes
Gave the router the ability to launch more than one router process, based on the config
Added a transport_error flag to C session to indicate a communcation error, which will prevent
    client sessions from hanging when making bad requests

git-svn-id: svn://svn.open-ils.org/OpenSRF/trunk@1253 9efc2488-bf62-4759-914b-345cdb29e865