Get rid of all usage of 'net_overlay' except for the specialized
tinc_host_conf action plugin, which generates the host
configuration. Result is also incidentally faster due to one less N^2
loop.

Move the infrastructure code to the 'float' subdirectory, preparing
for splitting it into a separate repository, but keep the ai-specific
stuff in the 'rules' directory as before.

Start adding LDAP support, and complete the frontend mail routing.