The scrape file was updated to only seek "rebar3"
tagged packages. There are too many Elixir-only
packages tagged as "make".

Templates now no longer use Make variables for substitution
but instead replace strings with their equivalent:

  template_name: Corresponds to n=template_name
  project_name:  Corresponds to $(PROJECT) or in=project_name

This allows defining templates outside of Makefiles. For
example an external plugin could define their templates
in templates/my_template.erl and then have the following
in the included Makefile:

  tpl_my_template = $(file < $(THIS)/templates/my_template.erl)

By default the created file will be in src/template_name.erl.
This can be overriden with the tplp_* variable:

  tplp_my_template = src/model/my_template.erl

Substitution is applied both to the template contents and
to its path.

In addition, attempting to overwrite an existing file when
creating a template will result in failure.

This method dates back from the beginnings of Erlang.mk
and should not have been used for around a decade by now.
Adding "git" to the offending dep lines is enough to upgrade.

This should both be more solid and more secure.

Erlang.mk will no longer feature packages out of the box,
except for the applications that we implement plugins for
(such as erlydtl, proper or relx) and the projects I work
on that are also used to test Erlang.mk (cowboy and friends).

This is a breaking change. In most cases the fix is to add
a full dep_* line for the dependencies that were used as
packages before.

The tests were waiting for the test group to finish before
they could continue with the next test group. Now "core"
and "all" targets directly depend on individual test cases,
allowing parallel Make to get to the next tests quicker and
removing 1/3rd of the total run time.

  make check -j8 -k  5790,16s user 1207,08s system 627% cpu 18:35,49 total
  make check -j8 -k  6250,13s user 1326,77s system 972% cpu 12:59,16 total