Windows Agent improvements

[conorbranagan]

This bug serves as aggregation of a bunch of issues with the current Windows Agent (3.6.3) and serves a list of things that must be fixed before releasing a new version.

• Change where the Windows Agent logs from the Event Viewer to multiple files, similar to how we do it on Unix systems but using the standard Windows log file paths.
• Test and fix the Windows status page. It seemed to be working fine in 3.8.0 but there were a bunch of bugs spammed from Tornado with the version upgrade. Better logging will make these issues more obvious.
• Make configuration locations more visible and obvious. Right now it's pretty tricky to install an integration because the config directory root (C:\ProgramData) is hidden by default. We could add some shortcuts to these directories, maybe adding a folder for the Datadog Agent in the Start menu that has these shortcuts?
• Better instructions for installing integrations. Right now we have all the example yaml files with *.yaml.example extensions. Our instructions don't really explain the process of editing these files very well and don't mention the status page at all (because it doesn't exist - yet).

Some additional tasks that would be nice-to-have but aren't as critical:

• (minor) Remove the UI installer from the build since we're not using it anymore.
• Add some sort of UI to the CLI installer for easy installation. (see Consolidate Windows UI and CLI installers. #344)
• (huge) Add a UI for configuring integration. Even something that just wraps the list of integration files and lets you edit them all from one little application.

[miketheman]

Included #496, #555

[remh]

Done with 3.9.1