Add a CodeFix for var -> specific type
Rename the new CodeFix
Add the analyzer for "'var' can be used"
Indicate when a variable name really is useless (Type cast)

The diagnostic "Use implicitly typed local variable declaration" now
have
two forms, one as a warning when the type is specified on the right and
one as an info if it isn't.
Manage the case where a cast is in parentheses
Shorter and cleaner code