[pgAdmin4][Patch]: RM #2214 PostgreSQL 10.0 compatibility (SCRAMauthentication support)

A new password encryption method "scram-sha-256" has been introduce in PostgreSQL10. Along with that a new method "PQencryptPasswordConn" has been exposed to get the encrypted password. This new method is not supported in "psycopg2". Ashesh has send the patch https://github.com/psycopg/psycopg2/pull/576 and has been merged into the master branch of psycopg2 and will be available in their next release 2.8

"Change password" functionality was not working, as pgAdmin4 not able to encrypt the password in scram. I have downloaded the latest code of psycopg2, compile it with libpq version 10 and implement the logic in pgAdmin4.

Attached is the patch to fix that issue. Please review it.     
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