[Alberta][autotools] Remove check for Alberta 2.

With autotool everything before Alberta 3 is no longer found.
[Alberta] Remove code paths for Alberta 2.

Alberta 2 is no longer supported. There is no deprecation
period as decided at the Dune Dev meeting 2014 in Berlin.
[CMake][Alberta] Remove support for pre-Alberta-3 versions.
Merge branch 'feature/fs1475-drop-pre-alberta3'