_devel_backend.sh: honor 'config.backend.file' option

* don't use `sed` for naive option parsing from JS
  use shell patterns
* prettyfy messages '^' means "beginnning of" as in BREs

Signed-off-by: Oleg Verych <olecom@gmail.com>
rbac fuse('/*/lib'): permission to access any app module's API

Signed-off-by: Oleg Verych <olecom@gmail.com>