RunConfiguration settings from application settings

[ssnenov]

Requirements

RunConfiguration should read application settings using ConfigurationManager. All settings read from AppSettings element should be stored in a collection (e.g. Dictionary<string, string> or NameValueCollection as it's in ConfigurationManager) in RunConfiguration class. Existing strongly typed settings also should read from AppSettings section if they aren't explicitly set.

In order to separate settings prepared for Html2Amp, the keys from AppSettings elements should be filtered. For example: all keys starting with "Html2Amp:".
The key name will be next after the prefix. For example: "Html2Amp:[key name]"
Example:

<appSettings>
    <add key="Html2Amp:RelativeUrlsHost" value="http://integration.mywebsite.com" />
</appSettings>

Why

This will enable Html2Amp to be easily extendable and continues integration friendly.