Remove user_env

For appcache, I needed to clarify what was the `user_env` variable and it seems it's useless now. 
Morever with the previous modification of apache conf, `main` it's not used anymore so it's a little bit weird to see we use it in some files (makefile, app.mako-dot-conf, index.mako.html).

So this PR remove the use of `main` and use the `apache_base_path` variable instead of `entry_path` and `print_entry` 

Possible `apache_base_path` values: ` `, `/[user_name]` or `/[branch_name]`

Test links:

[http://mf-geoadmin3.dev.bgdi.ch](http://mf-geoadmin3.dev.bgdi.ch)
[http://mf-geoadmin3.dev.bgdi.ch/ltteo](http://mf-geoadmin3.dev.bgdi.ch/ltteo)
[http://mf-geoadmin3.dev.bgdi.ch/fix_user_env](http://mf-geoadmin3.dev.bgdi.ch/fix_user_env)