Start using the install.sql file as base.

Do not build our own install.sql file anymore. This is not needed if we
only include the new functions in our new extension, in which case this
will always have to be loaded. This will simplify things.
Move back the FK contraint's into the tables as the order now can be
controlled.
Move out dependencies to be based upon pg version we are building
against. Also take architecture from building system.
Disable creating any functions in the extension except for the ones we
added.
Remove the last trace of the FK_CONSTRAINTS
Add documentation about the .deb packages
Make package name depend upon the version of postgres we are building
against
Roles should be in install.