Let's add some functionality for convinience of our users

[smtrfnv]

1. Provide a method to concatenate data from multiple ConstBuffers into one char buffer.
   int gather(char* buffer, size_t length, const ConstBuffer* buffers, size_t numBuffers)

2. Provide methods to append all ntsa buffer types to bdlbb::Blob, now there is only DataUtil::append(bdlbb::Blob *destination, const ntsa::Data& source) (which requires construction of ntsa::Data in advance)

3. Add ability to specify size of ConstBufferArray at construction (add ConstBufferArray(size_t initialSize, bslma::Allocator* basicAllocator = 0) constructor)