[ADD] base_external_system: Implement interface/adapter (#993)

* [ADD] base_external_system: Implement interface/adapter for external systems

* base_external_system: Fix OS model, add inherits, add validate

* base_external_system: Usability and private key pass

* base_external_system: Use contextmanager in adapter client

* base_external_system: Move contextmanager to interface

* base_external_system: Include contextmanager on adapter and system

* base_external_system: Unify client

* Use password widget for password field

* Add tests & security

* Fix lint

* Add plaintext note

base_external_system/__manifest__.py

@@ -0,0 +1,23 @@
+# -*- coding: utf-8 -*-
+# Copyright 2017 LasLabs Inc.
+# License LGPL-3.0 or later (http://www.gnu.org/licenses/lgpl.html).
+
+{
+    "name": "Base External System",
+    "summary": "Data models allowing for connection to external systems.",
+    "version": "10.0.1.0.0",
+    "category": "Base",
+    "website": "https://laslabs.com/",
+    "author": "LasLabs, Odoo Community Association (OCA)",
+    "license": "LGPL-3",
+    "application": False,
+    "installable": True,
+    'depends': [
+        'base',
+    ],
+    'data': [
+        'demo/external_system_os_demo.xml',
+        'security/ir.model.access.csv',
+        'views/external_system_view.xml',
+    ],
+}