[pgAdmin4][Patch] To fix the issues in Debugger module

Hi,

Please find patch to fix the below issues,

1) Debugger page layout
RM#2512

2) To fix the issue when you user clicks on Stop button and gets connection
lost error.
RM#2511

@Dave,
When we stop the debugger using pldbg_abort_target() function and try to
start it again in the same connection, we are not able to do so because we
do not get response from plugin(async query results shows busy status
only), I think that is the reason why in pgAdmin3 we have disable all the
buttons and release the connection if user clicks on stop button, For time
being I have done the same in pgAdmin4 until we find the solution for this
issue.

Misc changes are for PEP-8.

Please review.

--
Regards,
Murtuza Zabuawala
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company