Build Instructions suggestions

[dr-ratio]

Having recently followed the BuildInstructions.docx for Building the Player Framework Plugins section, I have some feedback.

• It may help to open with explaining why we're doing the batch build process, IE "This is a two step process where we will generate all the individual components first via a batch build, and then build the installers which package those up."
• The "deselect all and check the following projects" section is very long. It may be much faster and easier understand and follow by providing simpler instructions such as: Uncheck all entries whose names end with "Setup". Next, sort by "Platform" and uncheck all remaining entries which target the "Any CPU" platform. Now click "Build"
• Consider recommending to run VS as admin, as it may be needed to get past uninstalling previous versions, IE I ran into: "There was a problem uninstalling the extension with a VSIX identifier of "MSHLS.PF.Setup.99A0C51E-5EF9-485F-935B-0988930078F7". The extension 'Microsoft HLS Player Framework Plugins' requires administrative privileges in order to be uninstalled."

[dr-ratio]

• Also, building a list of additional SDK dependencies, with links to good download sites (or instructions for cases where Extensions and Updates is applicable, like for the Advertising SDKs), could save people a lot of hunting time. (Alternatively, adding dependencies to git may be worth consideration, where possible.)

[dr-ratio]

I can probably find time to make recommended changes for a PR this weekend, if you guys would like any of the listed changes. Let me know, thanks!