Feature/array mod

• fixed type definition within shared array, i.e. use size_type consistently instead of hard coded size_t
• fixed operator== for float types, in the previous version the comparison was made with fixed size tolerance, and cleaned-up implementation
• added unit tests for operator==
• replaced num_elements() with size() everywhere
• added deprecated L2 warning to num_elements

For reviewing purposes, only the following files have modifications other then num_elements() -> size():

• SharedArray.hpp
• testNekSharedArray.cpp
• NektarUnivConsts.hpp