single-threaded: registering handler requires name

When registering a handler against the single threaded component's
Endpoint/Notification object we now require a name to be provided in
order to make identifying handlers easier.

Add seL4SingleThreadedComponent templates

These templates extend the base camkes runtime to provide a single
threaded environment. CAMKES_PRE_INIT_MODULE_DEFINE and
CAMKES_POST_INIT_MODULE_DEFINE can be used to define similar pre_init
and post_init function hook functionality. The camkes run function is
used to block on a single endpoint with a bound notification for
receiving either notifications of synchronous messages.