Directly link objects to their source

[raviks789]

fixes #115

[julianbrost]

From trying out this PR (I haven't looked at the code at all): the incident view now shows all the information I expect with the changes from Icinga/icinga-notifications#98. So from that perspective, the remaining things are more or less cosmetic: that what's already mentioned in #115 (comment), but looking at the following screenshot also makes me ask how useful repeating the same object name and source icon over and over, given everywhere it's shown within one incident, it's the same.