ipalib: Allow multiple API instances

Merged the Registrar class into the Registry class. Plugins are now
registered globally instead of in ipalib.api and are instantiated per-API
instance. Different set of plugin base classes can be used in each API
instance.

https://fedorahosted.org/freeipa/ticket/3090

Reviewed-By: Tomas Babej <tbabej@redhat.com>

ipalib/frontend.py

@@ -27,7 +27,7 @@ from distutils import version
 from ipapython.version import API_VERSION
 from ipapython.ipa_log_manager import root_logger
 from base import NameSpace
-from plugable import Plugin, is_production_mode
+from plugable import Plugin, Registry, is_production_mode
 from parameters import create_param, Param, Str, Flag, Password
 from output import Output, Entry, ListOfEntries
 from text import _
@@ -40,6 +40,9 @@ from textwrap import wrap
 
 RULE_FLAG = 'validation_rule'
 
+register = Registry()
+
+
 def rule(obj):
     assert not hasattr(obj, RULE_FLAG)
     setattr(obj, RULE_FLAG, True)
@@ -366,6 +369,7 @@ class HasParam(Plugin):
         setattr(self, name, namespace)
 
 
+@register.base()
 class Command(HasParam):
     """
     A public IPA atomic operation.
@@ -1120,6 +1124,7 @@ class Local(Command):
         return self.forward(*args, **options)
 
 
+@register.base()
 class Object(HasParam):
     finalize_early = False
 
@@ -1278,6 +1283,7 @@ class Attribute(Plugin):
         super(Attribute, self)._on_finalize()
 
 
+@register.base()
 class Method(Attribute, Command):
     """
     A command with an associated object.
@@ -1364,6 +1370,7 @@ class Method(Attribute, Command):
             yield param
 
 
+@register.base()
 class Updater(Method):
     """
     An LDAP update with an associated object (always update).
@@ -1423,6 +1430,7 @@ class _AdviceOutput(object):
         self.content.append(line)
 
 
+@register.base()
 class Advice(Plugin):
     """
     Base class for advices, plugins for ipa-advise.