CB-4493 adding docs for installation from registry
[CB-3962] standardize 'splash screen'
[CB-3962] directory, not folder
[CB-3962] 'the FOO file', not 'the file FOO'
[CB-3962] add to stylesheet
Update README.md for simpler install instructions.
3.0 to 3.1 upgrading guide
[CB-4881] Change plugin to feature

- Change <plugin> to <feature> under <plugins-plist> section
[CB-4881] Update plugin to feature in plugin spec for edge.