pgAdmin 4 commit: Added support for the infrastructure for on demand ac

Added support for the infrastructure for on demand access/create the
server connection.

The BaseDriver and BaseConnection are two abstract classes, which allows
us to replace the existing driver with the currently used. The current
implementation supports to connect the PostgreSQL and Postgres Plus
Advanced Server using the psycopg2 driver.

Branch
------
master

Details
-------
http://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=e27e39a8f3b31a3e14bc56d473a01635228d0d8d

Modified Files
--------------
requirements.txt                                   |    1 +
web/config.py                                      |   52 +-
web/pgAdmin4.py                                    |   10 +-
web/pgadmin/__init__.py                            |   36 +-
web/pgadmin/about/__init__.py                      |    4 +-
web/pgadmin/browser/__init__.py                    |  137 +++--
web/pgadmin/browser/server_groups/__init__.py      |   89 ++-
.../browser/server_groups/servers/PPAS/__init__.py |   44 ++
.../server_groups/servers/PPAS/static/img/ppas.png |  Bin 0 -> 676 bytes
.../server_groups/servers/PostgreSQL/__init__.py   |   43 ++
.../servers/PostgreSQL/static/img/pg.png           |  Bin 0 -> 850 bytes
.../browser/server_groups/servers/__init__.py      |  453 +++++++++++++--
.../server_groups/servers/templates/css/node.css   |    7 +
.../servers/templates/css/servers.css              |   17 +
.../servers/templates/servers/password.html        |   19 +
.../servers/templates/servers/servers.js           |  346 ++++++++---
.../templates/server_groups/server_groups.js       |    2 +-
.../browser/templates/browser/js/browser.js        |   36 +-
web/pgadmin/browser/templates/browser/js/error.js  |    4 +-
web/pgadmin/browser/templates/browser/js/node.js   |  188 ++++--
web/pgadmin/browser/utils.py                       |  178 ++++--
web/pgadmin/misc/__init__.py                       |   12 +-
web/pgadmin/settings/settings_model.py             |   18 +-
web/pgadmin/static/css/overrides.css               |   33 +-
.../static/js/alertifyjs/pgadmin.defaults.js       |  114 ++++
web/pgadmin/static/js/backform.pgadmin.js          |   19 +
web/pgadmin/templates/base.html                    |    1 +
web/pgadmin/utils/ajax.py                          |   75 ++-
web/pgadmin/utils/crypto.py                        |   69 +++
web/pgadmin/utils/driver/__init__.py               |   33 ++
web/pgadmin/utils/driver/abstract.py               |  152 +++++
web/pgadmin/utils/driver/psycopg2/__init__.py      |  601 ++++++++++++++++++++
web/pgadmin/utils/driver/registry.py               |   84 +++
web/setup.py                                       |  167 +++++-
34 files changed, 2626 insertions(+), 418 deletions(-)