packages: make UCL files required
Modify template.ucl to require that the "all" UCL file exists for every
package. This prevents packages being added accidentally, and ensures
each package has as least a perfunctory comment and description.
Add missing UCL files for all existing packages.
Modify special packages created by Makefile.inc1 to pass the appropriate
parameters to generate-ucl to find their UCL files.
Reviewed by: des, bapt
Approved by: des (mentor)
Differential Revision: https://reviews.freebsd.org/D50281