[Feature Request] Reduce code analyzer's suggestion messages.

[filzrev]

Is your feature request related to a problem? Please describe.
When building docfx solution.
Currently about 2918 messages are shown on Visual Studio Error List window (When enable Build + Intellisense).

I want to reduce this suggestion messages because a lot of unneeded suggestions are reported.
And want to change some useful suggestion message level to warning. (e.g, performance related rules.)

Describe the solution you'd like
It needs following tasks to reduce suggestion messages.

• Fix code by refactoring
• Suppress message by code comment
• Suppress unrequired message by changing log level with .editorconfig settings.

I'll send PR to fix this issue.