Feature/captiveportal rework

Description
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- Cleaning up dispatcher
- Cleaning up httpd.portal config
- Better workflow in dispatcher
- Better handling of mobile captive-portal detection mecanisms
- Better handling of destination URL
- New configuration parameter for captive-portal detection mecanism URLs
- New configuration parameter for 'portal' interface type
- New configuration parameter for mod_status listening port on httpd.portal

Impacts
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- Captive portal flow...
-- Redirection when trying to reach an Internet resource while in registration
-- Redirection when trying to reach an Internet resource while in registration from a mobile device with captive-portal detection mecanism
-- Redirection when trying to reach an Internet resource while in registration using Google Chrome browser
- mod_status for httpd.portal
- httpd.portal vhost configuration depending on interface type
- More to come...

Not ready to be merged yet... Want feedbacks and point of view