[client-v2] Add support of working with large strings

[Paultagoras]

Problem: when data is read from stream it automatically decoded in most suitable form. It works well except with strings because it create overhead. Solution:

• store string as byte[] and convert on demand.
• let read strings as streams (this is for the case when someone storing images in String columns)

[AndrewRazumovskiy]

hello, any updates here?