How to install extension in offline environments, where Extension Downloader cannot connect to the Extension server

Installing an extension in offline analysis servers consists of the following steps:

1. Download the extension from https://extend.castsoftware.com/V2/ as an nupkg from a machine that has internet access
2. Copy the .nupkg to the analysis server using whatever mode is available
3. Use Extension Downloader as gui https://doc.castsoftware.com/display/EXTEND/Download+an+extension#Downloadanextension-guiUnpackthe.nupkgarchivefilewiththeCASTExtensionDownloaderGUI or in commenad line mode https://doc.castsoftware.com/display/EXTEND/Download+an+extension#Downloadanextension-cliUnpackthe.nupkgarchivefilewiththeCASTExtensionDownloaderCLI to unpack the extension. 
4. After above step verify that the unpackaged extension is found in your Extensions folder
5. Install the extension on the application database triplet using Server Manager following https://doc.castsoftware.com/display/EXTEND/Install+an+extension