Further improvements of dinrail::VectorProxy

[traversaro]

Even if we merge #3, I think we can improve the dinrail::GenericVector also further after that PR (especially until the code is actually used outside of this repo)

Possible open points:

• Descriptive name (Implement first prototype of dinrail::Device and dinrail::Parameters class #1 (comment))
• Improvements on how resize is handled (mentioned in person by @RiccardoGrieco)

fyi @RiccardoGrieco

[traversaro]

Descriptive name (Implement first prototype of dinrail::Device and dinrail::Parameters class #1 (comment))

This was fixed in #3 with the rename to dinrail::VectorProxy.