pgAdmin 4 commit: Ensure that null values handled properly in CSVdownl

Ensure that null values handled properly in CSV download. Fixes #3780

Branch
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master

Details
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https://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=41c028f944806b34fbfb06a0a146672aa1e18d2b

Modified Files
--------------
Make.bat                                           |   5 -
docs/en_US/images/preferences_sql_csv_output.png   | Bin 140688 -> 71521 bytes
docs/en_US/preferences.rst                         |   1 +
docs/en_US/release_notes_3_7.rst                   |   1 +
pkg/mac/build.sh                                   |   5 -
pkg/pip/setup_pip.py                               |   1 -
requirements.txt                                   |   1 -
web/pgadmin/tools/sqleditor/__init__.py            |   3 +-
.../sqleditor/utils/query_tool_preferences.py      |  11 +
web/pgadmin/utils/csv.py                           | 761 +++++++++++++++++++++
web/pgadmin/utils/driver/psycopg2/connection.py    |  43 +-
web/pgadmin/utils/preferences.py                   |  13 +-
12 files changed, 821 insertions(+), 24 deletions(-)