Ensure worspaces/pgadmin state is saved on abrupt shutdown of pgadmin.#GH_3319

[yogeshmahajan-1903]

No description provided.

[akshay-joshi]

GUI Review Comments:

1. When opening pgAdmin again in the browser Default Workspace should be in focus. Open Schema Diff tool and refresh the browser.

2. PSQL tools database name not showing in the single line on reopening pgAdmin.

3. Delete all the states from the table if the user changes the preferences and sets them to False.

4. Getting error AttributeError: 'NoneType' object has no attribute 'connection' in line 604, in _get_database_role psql/init.py

5. params['db'] = underscore_escape(data['db_name'])  TypeError: 'NoneType' object is not subscriptable in line 104 in psql/init.py

6. Open Query Tool/PSQL in the respective workspace and then refresh the browser. It opens in the Default workspace, which seems to be correct, but we need to document this behaviour.

7. Query Tool/PSQL for adHoc servers are still opening with error. We should not store state of the adHoc server.

8. The show_query_tool.js, show_erd_tool.js, showSchemaDiffTool.js and show_psql_tool.js files have duplicate code to open the respective tools. We can easily make some part of the logic generic.

9. Why file name 'showSchemaDiffTool.js' different in respect to others like show_query_tool.js

10. Documentation/Screenshot updates are missing for Preferences.

11. Create a new .rst file to explain this new feature.

12. Add comments in the new function added in this PR and wherever needed in the code, so that others can understand the logic.

[adityatoshniwal]

Have we handled the case where a server is removed?

[adityatoshniwal]

Last time I had asked if the connection was removed. Open query tool, disconnect server, remove the server and close the query tool.
Also, what happens to open files?