Enhance FastXmlElmentSplitter for use in Paratext merging
Change Xml splitter to return a class rather than a tuple
Also use Array.Copy rather than loop
(TimS): Changed ByteAccessor to use correct notation. Changed FastXmlElementSplitterTests to use the TempFile class.
(TimS): Changes based on reviewers comments (and added readonly to unchanged member variable).
Merge pull request #67 from sillsdev/ParatextXmlElementSplitter

Paratext xml element splitter