Use GPL-2.0-or-later as secondary license

Enforce TLS 1.2 for PowerShell downloader

https://github.com/blog/2507-weak-cryptographic-standards-removed

We can at least emit the URL of the repository and the path of the
resource which was attempted.

Fixes #2391.

Other minor changes:

* Use FSF-suggested wording in license description (added "as
  published by the Free Software Foundation")
* Update README.md and project.clj in resources/leiningen/template

Bump version of reply and clojure-complete

invoke GPG unattended with passphrase

Fixes #2387.

https://p.hagelb.org/no.gif

Refs #2364.

Fixes #2382.

Add project coordinate data to JAR metadata

This causes entries like:

    Leiningen-Project-ArtifactId: bar
    Leiningen-Project-GroupId: foo
    Leiningen-Project-Version: 1.2.3-SNAPSHOT

to be added to META-INF/MANIFEST.MF in JARS for projects with
project.clj files like:

    (defproject foo/bar "1.2.3-SNAPSHOT"
      ...
      )

Fixes #2373.

Bump the nREPL dep to 0.2.13

Closes #2370.

When this isn't present we should assume no files are on the bootclasspath.

Fixes #2369.

I guess that's self-explanatory. 0.2.13 is the latest stable version.

[docs] Update TEMPLATES.md to refer to resources dir rather than src dir

The current documentation claims template files live in src, rather than
resources - a fact trivially disprovable by either (a) referring to
Leiningen's default templates in resources/leiningen/new or (b) actually
trying to make a new template yourself.

This commit updates the documentation to refer to the correct directory.

Avoid "You have $CLASSPATH set" errors on upgrade

When we exec the newly downloaded leiningen script, it will replace our
current shell process and recalculate the classpath for us, so we can
safely unset this here. This avoids the new script throwing warnings
about the CLASSPATH variable being set (from the previous run) on
upgrades.

Fixed typos in doc.