Builds empty data sets.

Added the Build method and a unit test for build empty data sets.
Copies and concatenates data.

The DataBuilder can copy and concatenate byte arrays.
Appends ASCII strings.

You can append ASCII strings (not null terminated) to the data.
Appends different string encodings.

Supports ASCII, UTF-7, UTF-8, UTF-16 (little and big endian) and UTF-32.