Tidy :attributes: for all languages into sdk-common?

Sometimes we need to refer to another SDK - primarily libcouchbase (e.g. from PHP) or Java (from Scala et al).

These then need to be hardcoded like

xref:3.0@c-sdk:howtos:collecting-information-and-logging.adoc[here]. 

We could add these versions into sdk-common, meaning that updating version would only need to be done in one place, instead