describe repository template path expansions
add further clarification to template path rules
add some template expansion examples
clarify behavior of %subdirs%
suggestions from @jburel
suggestions from or inspired by @pwalczysko
clarification suggested by @manics
mention only relevant web servers
sysadmin web deployment cleanup
review of web deployment section, including:

 - splitting sysadmin and developers OMERO.web deployment
 - adjusting instructions for sysadmin
 - adjusting nginx instructions for developers
updating paths
adding static url
adding timeout adjustment
removing extra level of hierarchy
removing unnecessary configuration
fixing all inline comments from sbesson
exposing production deployment as the main option
reverting client_body_temp_path as needed
Merge pull request #848 from aleksandra-tarkowska/rebased/dev_5_0/nginx_doc

Nginx doc (rebased onto dev_5_0)
suggestions from @pwalczysko and @ximenesuk