Implemented CMS storage for user and nodes.

Implemented role and permission storage.
Introduced the CMS_PARTIAL_NODE and CMS_PARTIAL_USER.
Added support for node storage extension
  - storage of data specific to each node content type,
  - in addition to the core CMS_NODE)
  - For now, only implemented for SQL storage.
Note: in current version, CMS_PAGE support is hard coded in the core,
    (as opposed to be only supported by the node module.)
Commented/removed for now, the Web API code to update node summary, title, via REST request.

examples/demo/site/scripts/node.sql

@@ -0,0 +1,22 @@
+BEGIN;
+
+CREATE TABLE "nodes"(
+  "nid" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL CHECK("nid">=0),
+  "revision" INTEGER,
+  "type" TEXT NOT NULL,
+  "title" VARCHAR(255) NOT NULL,
+  "summary" TEXT NOT NULL,
+  "content" MEDIUMTEXT NOT NULL,
+  "author" INTEGER,
+  "publish" DATETIME,
+  "created" DATETIME NOT NULL,
+  "changed" DATETIME NOT NULL
+);
+
+CREATE TABLE page_nodes(
+  "nid" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL CHECK("nid">=0),
+  "revision" INTEGER,
+  "parent" INTEGER
+);
+
+COMMIT;