protocol
========

hello:

  c->s rcyn 1
  s->c yes 1

invalidate cache:

  s->c clear
  
test a permission:

  c->s test CLIENT SESSION USER PERMISSION
  s->c yes|no|VALUE [CACHING]

check a permission:

  c->s check CLIENT SESSION USER PERMISSION
  s->c yes|no|VALUE [CACHING]

erase (admin):

  c->s drop CLIENT SESSION USER PERMISSION
  s->c done|error ...

set (admin):

  c->s set CLIENT SESSION USER PERMISSION VALUE
  s->c done|error ...

list permissions (admin):

  c->s get CLIENT SESSION USER PERMISSION
  s->c item CLIENT SESSION USER PERMISSION VALUE
  s->c ...
  s->c done

enter critical (admin)

  c->s enter
  s->c done

leave critical (admin)

  c->s leave [commit|rollback]
  s->c done|error ...

register agent (agent):

  c->s agent NAME [ARGS...]
  s->c done|error ...

asking (agent ask CLIENT SESSION USER PERMISSION):

  s->c ask CLIENT SESSION USER PERMISSION
  c->s done | ([yes|no] [always|session|one-time])


----------------------------------------------------------
  c->s c(heck) CLIENT SESSION USER PERMISSION
  c->s d(rop) CLIENT SESSION USER PERMISSION
  c->s e(nter)
  c->s g(et) CLIENT SESSION USER PERMISSION
  c->s l(eave) [commit|rollback]
  c->s r(cyn)
  c->s s(et) CLIENT SESSION USER PERMISSION VALUE
  c->s t(est) CLIENT SESSION USER PERMISSION

  s->c clear
  s->c done
  s->c done [CLIENT SESSION USER PERMISSION VALUE]
  s->c done|error ...
  s->c item CLIENT SESSION USER PERMISSION VALUE
  s->c yes|no
  s->c yes|no|VALUE [CACHING]