Mark explicit versions earlier than our current default versions as deprecated

[danielrbradley]

In preparation for our next major release, we will remove API versions which are older than what's used in the default version.

The reason for removing these older versions is to reduce the size of each language's SDK and solve some associated performance issues.

This is not expected cause much disruption (if any at all) because:

• The majority of users just use the default version.
• Our understanding is that all features in previous API versions are also available in new versions (though the shape of the schema might change)
• The main motivation to use an explicit API version is to move to a version beyond the default version in order to use a new feature.

By depracating the older API versions we should be able validate these assumptions before moving to remove them in the next major release.