Allow use of non-numeric (e.g. UUID) values for ObjectIdentity.getIdentifier()

Prior to this commit, the ObjectIdentity id had to be a number. This
commit allows for domain objects to use UUIDs as their identifier. The
fully qualified class name of the identifier type can be specified
in the acl_object_identity table and a ConversionService can be provided
to BasicLookupStrategy to convert from String to the actual identifier
type.

There are the following other changes:

 - BasicLookupStrategy has a new property, aclClassIdSupported, which
 is used to retrieve the new column from the database. This preserves
 backwards-compatibility, as it is false by default.

 - JdbcMutableAclService has the same property, aclClassIdSupported,
 which is needed to modify the insert statement to write to the
 new column. Defaults to false for backwards-compatibility.

 - Tests have been updated to verify both the existing functionality
 for backwards-compatibility and the new functionality.

Fixes gh-1224

acl/src/main/resources/createAclSchemaPostgres.sql

@@ -15,13 +15,14 @@ create table acl_sid(
 create table acl_class(
     id bigserial not null primary key,
     class varchar(100) not null,
+    class_id_type varchar(100),
     constraint unique_uk_2 unique(class)
 );
 
 create table acl_object_identity(
     id bigserial primary key,
     object_id_class bigint not null,
-    object_id_identity bigint not null,
+    object_id_identity varchar(36) not null,
     parent_object bigint,
     owner_sid bigint,
     entries_inheriting boolean not null,