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.
Add error messages to localization file for salt provisioner
Fix salt provisioner error namespace to be more consistent with other provisioners
Merge pull request #2725 from MarcMeszaros/salt-i18n

provisioners/salt: provisioner missing error messages in localization file
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