Fix Bug 895930, first iteration of the new signature summary

@brandonsavage r? This is phase 1 of making signature summary's UI better. Looking at https://bugzilla.mozilla.org/show_bug.cgi?id=904614#c6 there is a small change needed on the server side to combine two of the tables, which will compact the UI further.

I have some additional ideas but, would like this to get merged first and then speak to KaiRo before moving forward.