pgAdmin 4 commit: Fixes issues specific to SYNONYMS

Fixes issues specific to SYNONYMS
- On droping a synonyms - the query should be modified in SQL pane.
- A proper message should be given on trying to drop an already dropped
  synonyms.
- Handle the synonyms with special characters.

Fixes #1607, #1608, #1609

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=689ef8d8d140783ea29030262d594bd2db962464
Author: Murtuza Zabuawala <murtuza.zabuawala@enterprisedb.com>

Modified Files
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.../servers/databases/schemas/synonyms/__init__.py | 38 +++++++++++++++++-----
.../templates/synonym/sql/9.1_plus/create.sql      |  8 +++--
web/pgadmin/browser/templates/browser/js/node.js   |  4 +--
3 files changed, 38 insertions(+), 12 deletions(-)