Bump to acts 0.8.2

This should (probably) go in after !444 (closed)

Acts v0.8.2 changes this w.r.t to the previous version:

• Change interface of tracking geometry builder to allow easier integration with athena tools. (std::function)
• Include first version of a billoir vertex fitter
• Measurement "identifiers" are now referred to as "source links"
• Switch to C++17 as minimum required standards version