Automatically add HTTP schema to URL when it is missing

[cweiske]

Is your feature request related to a problem? Please describe.
I copied the URL 192.168.3.8:9227 I used with curl into the dejavu connect URL box and wondered why it did not work.
It turned out that dejavu requires the http:// schema.

Describe the solution you'd like
dejavu should automatically prepend the http:// schema to the URL if it has no schema.

[siddharthlatest]

This would be good to have.

[quangdutran]

@siddharthlatest I have created a PR for this issue: #496
Could you review it? thank you