pgAdmin 4 commit: Fixes few issues with File Manager.

Fixes few issues with File Manager.

- Rename file/folder not working in list view.
- Selection folder only should not allow to select file.
- Ui changes in table list to match with the pgadmin color styles.
- Custom STORAGE_DIR path don't list files/folders when opened in window
  system.
- Code cleanup, formatting & did proper commenting.
- In file selection mode, the value typed in text box not setting into
  backbone model.
- Removed create file code, it should be handled on module using it.
- Written a common function to make ajax request, instead of writing
  individual functions for same task.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=3120ce190928d2f87e19d11d7e39086fefd8d2bf
Author: Surinder Kumar <surinder.kumar@enterprisedb.com>

Modified Files
--------------
web/pgadmin/misc/file_manager/__init__.py          |  36 +-
.../misc/file_manager/static/css/file_manager.css  |  85 ++-
.../templates/file_manager/js/file_manager.js      |  55 +-
.../templates/file_manager/js/utility.js           | 669 ++++++++-------------
web/pgadmin/static/js/backform.pgadmin.js          |  29 +-
5 files changed, 349 insertions(+), 525 deletions(-)