Added Choose the template paragraph

[mrizzi]

Added Choose the template paragraph
Changed the sample commands to use the web-template-empty-dir-executor.json template

I think it's useful, to evaluate the final result, to have a look also the the rendered file in my branch https://github.com/mrizzi/windup-openshift/blob/WINDUP-2258-readme/README.md

This depends on #10

[PhilipCattanach]

I think it would be better we used the all capitals REST acronym.
Regarding the web-template.json 'but it requires more persistent volume resources since it adds a persistent volume also to the executor pod'. It is not clear what benefit the persistent volume to the executer pod brings. Why would a user choose to use this template over the recommended one? If there isn't a good reason for retaining it perhaps we should consider deleting it.