Remove view and iterator support if exceptions are not used

[vvish]

As there is no generic way to propagate error from standard algorithms and views, usage of custom input iterators that can fail can be unsafe.

It is required to enable methods returning views conditionally, if exceptions are used.
If exceptions are not used method template receiving functor can be used instead ( tx.iterate_by_key(key, print_item); ).

The task is dependent on #9