pgAdmin 4 commit: Add the ability to import and export serverdefinitio

Add the ability to import and export server definitions from a config database. Fixes #3772

Branch
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master

Details
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https://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=f0327f5219a7964d4ee43a9154ba6811fb8f04d3

Modified Files
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docs/en_US/connecting.rst                          |  26 +-
docs/en_US/export_import_servers.rst               | 117 +++++++
docs/en_US/release_notes_3_6.rst                   |   2 +
web/pgadmin/setup/tests/__init__.py                |   8 +
web/pgadmin/setup/tests/servers.json               |  41 +++
.../setup/tests/test_export_import_servers.py      |  48 +++
web/servers.json                                   |  20 ++
web/setup.py                                       | 358 ++++++++++++++++++++-
8 files changed, 606 insertions(+), 14 deletions(-)