Simple Subnets: disable presence validation for gateway

fixes BZ #1153116
Merge pull request #350 from ifarkas/simple_subnets-delete_gateway_presence_validation

Simple Subnets: disable presence validation for gateway
Fixes BZ#1152655 - increases width of All Details modal and spacing
Merge pull request #351 from knowncitizen/bz1152655

Fixes BZ#1152655 - increases width of All Details modal and spacing
Version 0.4.6