Catch static-ness changes and sealing classes

[Youssef1313]

I'm submitting a...

Feature request

Current behavior

1. Adding/removing a static keyword to a member (class, method, property, ...) is not detected.
2. Adding sealed modifier to a member is not detected.

Expected behavior

Should be detected. Note that removing sealed modifier should be fine. Only adding it is a breaking change that we want to catch,

Minimal reproduction of the problem with instructions

Environment

Package Version(s): 

Visual Studio
- [ ] 2017 (version: )
- [ ] 2017 Preview (version: )
- [ ] for Mac (version: )