OMERO configuration properties

This PR :
- reviews the source code links to `et/comero.properties` across the documentation
- replaces them by links to the `sysadmins/config` page whenever appropriate
- review all references to the server configuration properties and uses the `:term:` markup when possible
Sorry, right. THere are two dots in  ```omero.ldap..```. Either could you add start ```omero.ldap.*.``` or remove one dot?