[pgAdmin4][Patch]: SQL Auto completion feature for Query Tool

Hi All

I have implemented the sql auto complete feature for Query Tool in
pgAdmin4. To achieve this I have analyzed the code of "*pgcli (*http://pgcli
.com/)" and also used some part of the code "(https://github.com/dbcli/pgcli
*)*" with our own modification.

"pgcli" buffers all the data(databases, tables, functions etc...) at once
while connecting to the database, but we can't do that, so when user press "
*Ctrl+Space*" in the Query Tool we will fetch the data and display the
suggestions accordingly.

Attached is the patch file. Please review it and let me know the review
comments (if any).

--
*Akshay Joshi*
*Principal Software Engineer *

*Phone: +91 20-3058-9517Mobile: +91 976-788-8246*