Improve TemplateVec class

Mainly cleaning up the code and simplifying some of the internals. The current state show some deficiencies. The implementation is relying on unique ids for example. And it is modifying objects (_data_vec) which were not created by TemplateVec. This is potentially dangerous in terms of data consistency and memory leaks.

I think that this code is used by the gui. Can someone check if the gui is still working for them please?

I started using some of the harmless c++11 features like auto. This pull request is also for checking the c++11 standard compatibility.