snapcraft 2.16 has been released

[Sergio Schvezov]

Hello snapcrafters!

We are pleased to announce the release of version 2.16 of snapcraft:
https://launchpad.net/snapcraft/+milestone/2.16

The highlights in this release are:

- New variables available to be used within `snapcraft.yaml` and also 
exported in the environment during plugin runs: 
`SNAPCRAFT_PROJECT_NAME`, `SNAPCRAFT_PROJECT_VERSION`, 
`SNAPCRAFT_PART_INSTALL` (specific to the part where it is used) and 
`SNAPCRAFT_STAGE` (now also exported in the environment).
- `snapcraft register --private` can now be used to register private snaps.
- A `grade` of `stable` or `devel` can be set in `snapcraft.yaml` which 
would gate any accidental releases to the `stable` and `candidate` channels.
- `snapcraft cleanbuild --debug` will drop you in a shell if errors are 
encountered.
- Filesets can now recursively glob, allowing constructs like `**/*.pyc`
- The `ant` plugin now allows parameters.

This release has seen many contributions from outside of the snapcraft
core team, so we want to give a shout out to these folks, here's a team
thank you for:

- Caio Begotti
- Evan Dandrea
- Loïc Minier
- Scott Moser

To consume the latest snapcraft release on Xenial Xerus (16.04), we
suggest you install the snapcraft package from the Ubuntu Archives:

     sudo apt update
     sudo apt install snapcraft

To get the source for this release check it out at
https://github.com/ubuntu-core/snapcraft/releases/tag/2.16

A great place to collaborate and discuss features, bugs and ideas on
snapcraft is snapcraft at lists.snapcraft.io mailing list or directly in
the #snappy channel on irc.freenode.net.

To file bugs, please go to https://bugs.launchpad.net/snapcraft/+filebug.

Happy snapcrafting,
-- Sergio and the team