Extend changeserver command to allow change of servers

[prasadtalasila]

Description

The changeserver sub-command of prefs command only changes the main server, but not the gitlab server. We need to change the gitlab and mainserver separately and together.

Steps to Reproduce

1. Run autolabjs prefs changeserver command

Expected behavior: [What you expect to happen]
The command allows changing of mainserver and gitlab host name / IP addresses.

Actual behavior: [What actually happens]
The command allows changing of only mainserver.

Reproduces how often: [What percentage of the time does it reproduce?]
Everytime autolabjs prefs changeserver is run.

[prasadtalasila]

PR #88 closes the issue.