Merge branch 'release-0.14'
Bump version to 0.15rc1

Add multiple version files to automatically update the docs version too.
We need devflow 0.13rc1 or later for this to work
Update ChangeLog for version 0.15rc1
Add pithos backend version check

Synnefo version 0.15.1 has introduced a selectable storage backend
for Pithos, resulting in necessary changes to the ModularBackend class.
In order to keep backward compatibility with older Synnefo versions,
we check the Pithos backend version and instantiate the ModularBackend
class appropriately.
Bump version to 0.15rc2

Update Changelog and version files.
pithcat: Remove default option values

Handle better possible backend options and require necessary
ones by printing appropriate error messages.
Fix typos in error messages and docs

Replace all references of `environmental variable' with `environment
variable'
Bump version 0.15rc3

Update ChangeLog and version files
Merge branch 'release-0.15'
Bump version 0.15

Update ChangeLog and version files for snf-image 0.15
Bump version to 0.15next