use lambda-sort, drop old custom code

 the lambda sort function requires -std=c++0x or -std=gnu++0x,
           // first supported in gnu 4.5, but our usage here busts in 4.5.2
           // and may first work in 4.6, not yet available pre-packaged for
           // Ubuntu 11.04.

requires c++0x and later and gcc 4.5+ which is now ok
Revert "use lambda-sort, drop old custom code"

This reverts commit 1083a775e34f728684ee86bb79cdcd033357f7b0.
drop dead code

since 2011, _learnActivity.add(...)
StringUtils: remove unused code toDouble()

was #if 0 ...
Merge pull request #313 from breznak/cleanup-deadcode

Cleanup deadcode