Update Sendfile Code for NGINX

This will send **/WEBROOT**/data/**FILEPATH** to NGINX, **FILEPATH** can be..

1. files/RELATIVE-PATH = "Common Files"
2. personal/**USER**/RELATIVE-PATH = "My Files"
3. **WORKSPACE**/RELATIVE-PATH = "Additional FS Workspaces"


NGINX Config Changes 
----
```
location ^~ /data {
    internal;
#    location /data/ADDITIONAL-FS-WORKSPACE {
#        alias /PATH/TO/ADDITIONAL-FS-WORKSPACE;
#    }
}
```
**fastcgi_param X-Accel-Mapping** in no longer needed and can be removed.

----
This respects non-default webroots (e.g. http://example.com/pydio) avoiding location conflicts in NGINX config files.  It also works for multiple workspaces unlike the previous method.  Fixes https://github.com/pydio/pydio-core/issues/501