sepolicy: Add write_logd, read_logd & control_logd

- Add write_logd, read_logd and control_logd macros added along
  with contexts for user space logd.
- Specify above on domain wide, or service-by-service basis
- Add logd rules.
- deprecate access_logcat as unused.
- 'allow <domain> zygote:unix_dgram_socket write;' rule added to
  deal with fd inheritance. ToDo: investigate means to allow
  references to close, and reopen in context of application
  or call setsockcreatecon() to label them in child context.

Change-Id: I35dbb9d5122c5ed9b8c8f128abf24a871d6b26d8