Reduces use of split infinitives.

Some would argue that split infinitives can be considered to be correct,
but the issue in these cases is that the phrasing is a bit smoother
without them.
core: More informative error if plugin.json parsing fails
Correcting the name and url for the Dockerfile instruction that sets the default command to run in an image
guests/linux: Emit upstart event `vagrant-mounted` also on NFS mounts

Complements #2502, and fixes error on VMs without upstart (like #2596).
guests/linux: Emit upstart event on VirtualBox using the expanded path
core: Log loaded plugin versions

One more piece of information to help support.
website/docs: document "create" option for synced folders [GH-2730]
core: handle EOFError when checking checksum [GH-2716]
hosts/bsd: check exports only if exports file exists [GH-2714]
Merge pull request #2713 from tmatilai/log_plugin_versions

core: log loaded plugin versions
style
Merge pull request #2705 from tmatilai/upstart-emit-nfs

Emit upstart event `vagrant-mounted` also on NFS mounts
Update CHANGELOG
Merge pull request #2697 from Ninjamoose/dockerCmdCorrection

website/docs: CMD command correction
Merge pull request #2693 from oalders/master

core: reduces use of split infinitives.
commands/plugin: use default version requirement
Merge pull request #2694 from tmatilai/plugin-json-errors

core: show more informative error if plugin.json parsing fails
Update CHANGELOG