Geo: Added `gitlab:geo:check` and improved `gitlab:env:info` rake tasks
This MR implements in the info task:
- Detect and display proxies defined on the OS (by specific env variables)
Display environment variables
A new rake task was created to diagnose Geo (#76 (closed)):
- Detect if license allows to use Geo
- Detect if Geo is enabled in the system
- Detect if Geo can reach it's nodes (primary and secondary)
Closes #1611 (closed)