Add manual about template creation

Author: drwatson1

ProjectTemplates/How to create new template.md

@@ -0,0 +1,20 @@
+# How to create new template
+
+After making any changes do:
+
+1. Select Release configuration for a solution
+1. Select ReferenceProject in "Solution Explorer"  and click "Project/Export Template..." menu item from the VS main menu
+1. In the appeared dialog box select "Project template" option and "ReferenceProject" in the combobox below and click Next
+1. Set the value "ASP.Net WebAPI Application with OWIN" as a template name
+1. Clear checkbox "Automatically import the template into Visual Studio" if you don't want immediately import it and click Finish button
+1. Extract all files from the created zip-archive to any folder as you want. Typically, the file can be found in "C:\Users\<YOU>\Documents\Visual Studio 2017\My Exported Templates" folder
+1. Open ReferenceProject.csproj file in any text editor and find "DocumentationFile" tag
+1. Replace string "%24safeprojectname%24" to "$safeprojectname$" inside it and save the file
+1. Replace a file "MyTemplate.vstemplate" with the one from the project folder with the same name
+1. Add all files from the folder to zip-archive with a name "ASP.Net WebAPI Application with OWIN.zip"
+1. Copy this file to "ProjectTemplates\AspNet.WebApi\ReferenceProject\ReferenceProjectVSIX\ProjectTemplates\CSharp\Web" folder and replace an existing one
+1. Go to VS, expand a ReferenceProjectVSIX project and double click on source.extension.vsixmanifest file
+1. Increase minor version number on the tab "Metadata" in the top right corner
+1. Rebuild the ReferenceProjectVSIX project and get "ASP.Net WebAPI Application Project Template.vsix"
+
+That's all. "ASP.Net WebAPI Application Project Template.vsix" can be uploaded to VS Marketplace or installed in VS.