cxx::vector support of Capacity 0 and erase by index

## Brief feature description

1. cxx::vector shall support "0" as Capacity
2. cxx::vector shall allow to erase an element identified by its index, i.e., new method `iterator erase(uint64_t index)`

## Detailed information

1. Support for Capacity 0 makes the cxx::vector implementation more generic. Typically, the capacity is given as configurable compile-time constants. Such a constant might potentially be set to "0", which shall not break compilation.
2. The existing `iterator erase(iterator position)` method assumes that iterators are used. In case the vector is accessed via index, a new `iterator erase(uint64_t index)` method is more convenient.