Support a fallback to an empty result-set when a csv file is missing

[Seddryck]

At the moment when a csv file referenced in a test is not existing, an ExternalDependencyNotFound exception is generated and the test is in error. This is a limitation in some cases where you'd expect that your test would consider your file as an empty file. Considering your file as empty could be not enough if you're using column names. In that case it would be helpful to be able to redirect to another file with just the model (columns' name).

<result-set>
  <file>
    <path>...</path>
    <if-missing behavior="redirect">
       <file> 
           <path>...</path>
       </file>
    </if-missing>
  </file>
</result-set>

or (default value ... shouldn't be serialized)

<if-missing behavior="error">

or

<if-missing behavior="empty">

[Seddryck]

• Support for file as an element (and still support an attribute) at the XML level
• Support for optional XML element parser with an attribute name
• Handle of element parser as an alias for the previous file.txt!parserName
• Support for optional XML element if-missing
• Implement redirection behavior

[Seddryck]

Beta-available at https://ci.appveyor.com/project/Seddryck/nbi/builds/22703377/artifacts

[Seddryck]

Added support for parser at https://ci.appveyor.com/project/Seddryck/nbi/builds/23349873/artifacts