Documentation for Standalone configuration upgrade needs to be improved and fixed

As it is currently, the documentation is difficult to navigate and is somewhat incomplete for upgrading Couchbase Server for standalone configuration. 

In particular, the "Performing the Single Node Upgrade" chapter needs to be more detailed:

• the procedure just refers the user to  "see the section Installing Couchbase Server appropriate for your platform for detailed installation instructions." But the information found there is of no use, as the user will eventually be guided and land back on the "Performing the Single Node Upgrade".

• Also , the procedure should cover Windows:

• the path provided in Step 3 is only for Linux users, and is not helpful for Windows users) 
• there should be a step to instruct the user to uninstall the previous version, otherwise the upgrade fails