Revert "Revert "Revert "v4l2 - update handler, source resolution change, control of secondary instance creation"""

This reverts commit 1e7831b78f0ce1c98aac874e5bc8c77a48bb748b.
Revert "v4l2 -  1)update handler 2)source resolution change 3) control of second instance creation"

This reverts commit 6d889d94298a183c14d7c3f9db1ae6cfda8c07fd.

	modified:   include/baresip.h
	modified:   modules/v4l2/v4l2.c
	modified:   src/config.c
	modified:   src/core.h
	modified:   src/stream.c
	modified:   src/ua.c