libostree v2019.1

[Colin Walters <walters verbum org>]

https://github.com/ostreedev/ostree/releases/tag/v2019.1

This is the first libostree release of 2019; no big changes, just a collection of smaller
features and bugfixes.  

On the features side, a good example is:
`lib/repo: Search a list of paths in gpgkeypath for gpg keys`
from PR #1773 - this will be useful for Fedora which rotates GPG keys
across releases.

Another feature is `grub2: add support for devicetree`
from PR: #1790

`lib/kargs: allow empty-list arguments` i.e.  PR #1785 is between a
bugfix and feature - it ensures libostree supports "empty list" kernel
arguments.

There's also some ongoing work to have libostree be a "backend"
for OCI/Docker container storage; `checkout: honor opaque checkouts`
in PR #1486 is part of that.

`pull: If built with --disable-http2, allow enabling via http2=1` from
PR #1798 will allow people to more easily play with HTTP2 if
it's disabled by default.

Thank you to all contributors!

```
Alexander Larsson (1 PR, 1 commit)
  Fix leak in ostree_content_stream_parse() (#1784)

Colin Walters (6 PRs, 8 commits)
  lib/commit: Try checksum+hardlink for untrusted local same-uid repos (#1776)
  Update libglnx (#1781)
  ci/papr: Drop insttests (#1783)
  pull: If built with --disable-http2, allow enabling via http2=1 (#1798)
  PR: #1766
    ci: Add `dist-then-build` target to catch missing `EXTRA_DIST`
    build-sys: Dist ostree-finalize-staged.path
  PR: #1800
    Post-release bump
    Release 2019.1

Giuseppe Scrivano (1 PR, 1 commit)
  checkout: honor opaque checkouts (#1486)

Jonathan Lebon (7 PRs, 7 commits)
  bin/refs: Disallow creating broken aliases (#1768)
  bin/pull-local: Add --commit-metadata-only (#1769)
  lib/commit: Copy user.ostreemeta only for bare-user (#1771)
  lib/commit: Add devino_cache_hits to txn stats (#1772)
  bin/pull: Add URL metavar for --url switch (#1782)
  boot/grub2: Add some more explanation in ostree-grub-generator (#1791)
  PR: #1761
    ostree/main: Wrap `Version` in `--version` in quotes
    (and 1 commit from other author)

Luca Bruno (1 PR, 1 commit)
  lib/kargs: allow empty-list arguments (#1785)

Matthew Leeds (1 PR, 1 commit)
  lib/repo: Clarify docs for importing w/ trust (#1777)

Matthias Clasen (1 PR, 2 commits)
  PR: #1788
    Fix a small leak in ostree_repo_remote_list_collection_refs
    Fix a small leak in ostree_repo_pull_with_options

Rafael Fonseca (2 PRs, 2 commits)
  admin/status: Correctly check GPG signature (#1787)
  admin/status: test GPG signature check (#1797)

Ricardo Salveti (1 PR, 1 commit)
  grub2: add support for devicetree (#1790)

Sinny Kumari (1 PR, 1 commit)
  atomic-upgrades doc: fix example url to fetch a ref checksum (#1795)

Umang Jain (3 PRs, 3 commits)
  lib/repo-commit: Relax min-free-space check in prepare_transaction() (#1779)
  man/ostree.repo-config: Update min-free-space-* docs (#1786)
  PR: #1761
    Post-release version bump
    (and 1 commit from other author)

rfairley (1 PR, 1 commit)
  lib/repo: Search a list of paths in gpgkeypath for gpg keys (#1773)
```