When g_option_context_parse fails, context and error variables are not getting free'd
which results in memory leaks. Free'ing the same.
And replacing g_error_free with g_clear_error, which checks if the error being passed
is not NULL and sets the variable to NULL on free'ing.
https://bugzilla.gnome.org/show_bug.cgi?id=753854
The channel property allows multiple intersrc/sink pairs to find
each other. It's a free-form text string that must match among
various inter elements. Also fixed up documentation and latency
handling.