Introduce QArrayDataOps::appendInitialize

Introduce QArrayDataOps::appendInitialize

Adds given number of default-initialized elements at end of array. For
POD types, initialization is reduced to a single memset call. Other
types get default constructed in place.

As part of adding a test for the new functionality the arrayOps test was
extended to verify objects are being constructed and assigned as
desired.

Change-Id: I9fb2afe0d92667e76993313fcd370fe129d72b90
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>