Pin default version to v1.0.0

[ccremer]

Both exoscale and cloudscale module versions have a v1
This is to prepare the component for another v1 release that has a default version parameter to something that is considered current "master" branch before introducing breaking changes.

After such release, the version can be bumped to v2.0.0 for the cloudscale provider.

Should be merged before #12

Checklist

• Keep pull requests small so they can be easily reviewed.
• Update the documentation.
• Categorize the PR by setting a good title and adding one of the labels:
  bug, enhancement, documentation, change, breaking, dependency
  as they show up in the changelog

[ccremer]

@simu
The cloudscale and exoscale terraform repos don't have a documentation module where I could document the upgrade process.
Is this repository the right place to do it? It already has how-to pages for those providers

[simu]

It's probably fine to document the TF module upgrade process in this repo, since the modules themselves are currently not really documented properly.

[ccremer]

I propose to add the upgrade documentation as part of #12