Replace Select and Merge SelectMany

[Back to Code Analysis & Inspection] (https://github.com/oriches/Resharper.ReactivePlugin/wiki/Code-Analysis-&-Inspection)

Adds a hint highlight to Rx method calls Select & Merge which can be replaced by a single call to SelectMany- it is short hand for calling Select then followed by Merge.

source.Select(selector).Merge();

can be replaced by

source.SelectMany(selector);