Fix typos and code style (microsoft#741)

* Fix filename containing a space (`ApiKeyAuthenticationHandler .cs`)
* Fix typos
* Fix code style
* Add missing rule for local constants
* Add commented code to automate code style checks. These don't work
with .NET Standard 2.0, so we'll need some extra research.
* Fix one incorrect ILogger naming
* Add some TODOs about unused code
* Fix xmldocs

Author: dluc

.editorconfig

@@ -131,12 +131,17 @@ dotnet_diagnostic.CA2201.severity = warning # Exception type System.Exception is
 
 dotnet_naming_style.pascal_case_style.capitalization = pascal_case
 
+dotnet_naming_style.camel_case_style.capitalization = camel_case
+
 dotnet_naming_style.static_underscored.capitalization = camel_case
 dotnet_naming_style.static_underscored.required_prefix = s_
 
 dotnet_naming_style.underscored.capitalization = camel_case
 dotnet_naming_style.underscored.required_prefix = _
 
+dotnet_naming_style.uppercase_with_underscore_separator.capitalization = all_upper
+dotnet_naming_style.uppercase_with_underscore_separator.word_separator = _
+
 dotnet_naming_style.end_in_async.required_prefix =
 dotnet_naming_style.end_in_async.required_suffix = Async
 dotnet_naming_style.end_in_async.capitalization = pascal_case
@@ -148,6 +153,10 @@ dotnet_naming_symbols.constant_fields.applicable_kinds = field
 dotnet_naming_symbols.constant_fields.applicable_accessibilities  = *
 dotnet_naming_symbols.constant_fields.required_modifiers = const
 
+dotnet_naming_symbols.local_constant.applicable_kinds = local
+dotnet_naming_symbols.local_constant.applicable_accessibilities  = *
+dotnet_naming_symbols.local_constant.required_modifiers = const
+
 dotnet_naming_symbols.private_static_fields.applicable_kinds = field
 dotnet_naming_symbols.private_static_fields.applicable_accessibilities = private
 dotnet_naming_symbols.private_static_fields.required_modifiers = static
@@ -161,9 +170,13 @@ dotnet_naming_symbols.any_async_methods.required_modifiers = async
 
 # Rules
 
-dotnet_naming_rule.constant_fields_should_be_pascal_case.severity = error
-dotnet_naming_rule.constant_fields_should_be_pascal_case.symbols  = constant_fields
+dotnet_naming_rule.constant_fields_should_be_pascal_case.symbols = constant_fields
 dotnet_naming_rule.constant_fields_should_be_pascal_case.style = pascal_case_style
+dotnet_naming_rule.constant_fields_should_be_pascal_case.severity = error
+
+dotnet_naming_rule.local_constant_should_be_pascal_case.symbols = local_constant
+dotnet_naming_rule.local_constant_should_be_pascal_case.style = pascal_case_style
+dotnet_naming_rule.local_constant_should_be_pascal_case.severity = error
 
 dotnet_naming_rule.private_static_fields_underscored.symbols = private_static_fields
 dotnet_naming_rule.private_static_fields_underscored.style = static_underscored