pgAdmin 4 commit: Resolved quite a few file-system encoding/decoding re

Resolved quite a few file-system encoding/decoding related cases.

In order to resolve the non-ascii characters in path (in user directory,
storage path, etc) on windows, we have converted the path into the
short-path, so that - we don't need to deal with the encoding issues
(specially with Python 2).

We've resolved majority of the issues with this patch.
We still need couple issues to resolve after this in the same area.

TODO
* Add better support for non-ascii characters in the database name on
windows with Python 3
* Improve the messages created after the background processes by
different modules (such as Backup, Restore, Import/Export, etc.),
which does not show short-paths, and xml representable characters for
non-ascii characters, when found in the database objects, and the file
PATH.

Fixes #2174, #1797, #2166, #1940

Initial patch by: Surinder Kumar
Reviewed by: Murtuza Zabuawala

Branch
------
master

Details
-------
http://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=f2fc1ceba884d56307e69e2febd6035f6f248995

Modified Files
--------------
web/config.py | 45 +++--
web/pgAdmin4.py | 8 +-
web/pgadmin/__init__.py | 14 +-
web/pgadmin/misc/bgprocess/process_executor.py | 243 +++++++++++++++----------
web/pgadmin/misc/bgprocess/processes.py | 90 +++++----
web/pgadmin/tools/backup/__init__.py | 109 ++++++-----
web/pgadmin/tools/import_export/__init__.py | 167 +++++++++--------
web/pgadmin/tools/restore/__init__.py | 78 ++++----
web/pgadmin/utils/__init__.py | 102 +++++++++++
web/pgadmin/utils/driver/psycopg2/__init__.py | 10 +-
web/pgadmin/utils/html.py | 11 +-
web/pgadmin/utils/paths.py | 6 +-
web/pgadmin/utils/preferences.py | 2 +-
web/pgadmin/utils/session.py | 5 +-
web/setup.py | 71 +++++---
15 files changed, 599 insertions(+), 362 deletions(-)