Autodetection of local gateway port

[RubenKelevra]

Current situation

Currently the user has to enter the gateway address if it's different than the default http://localhost:8080. Since 8080 is often used as default, this might clash with other services, so it's common to change this in the settings, requiring to config the IPFS companion as well.

Feature request

Since the IPFS companion could auto-detect this by fetching the config from the running ipfs-daemon instead of having the user to enter the same info in two places.