+ sentences and paragraphs to metadata section

first pgph on what metadata is, few specifics.
added some citations to the metadata section

Michener 1997
Zimmermand 2003
deleted notes for metadata section, expanded paragraphs
added more refs and paragraphs to metadata section
added reichmann and whitlock refs to metadata section
adding paragraphs to the quality control section
delete notes and expand paragraphs in quality control section
added citation Lampe 1998 to quality check section
added a sentence on imp. of having metadata to metadata section
added a ref to the metadata section - Fraser & Gluck 1999
Added text to the Data Sharing section
Added year to the Palmer reference
Added text to the standard structure section
Adds paragraphs with introduction and recommendations for null values section.
Starting to get null values table added.
Null values table fully added, may require some further tweaks.
Adds standard format section.  Figure will follow in a separate file.
Adds file of draft of standard formatting errors figure.
Merge pull request #3 from embaldridge/format_nullvalues

Format null values
Initial draft of Introduction