Improve error messages on config load
Parametrize most of the paths in the Makefile

Put the folder names into variables and make them relative to the
root folder of the git checkout.
Start reorganizing the files of the framework (WIP)

Beware that due to the changing paths, some things are still broken.
Next commits will try to get the situation back to normal
Copy the front controller to the build root folder
Move location of framework's generated config
Clean the build folder on the main clean target
Fix the paths in the code
Fix template path
Move around some more files
Better explain the example site
Fix DB-related build commands
Fix site's specific clean target

Use the Makefile from the source folder instead that always exists.
The one in the build folder could be inexistent at that point, or
belonging to a different site.
Log the request IP
Fix output file base path