Include QA/QC statement in README.txt.
Update final export panel.

* Add QA/QC text.
* Imply email is required.
* Update export instructions
Update download email

* Add QA/QC statement.
* Add citation.
Replace data description files

Replace .xlsx and product guide with unified
Imiq_DataDescription_README.pdf.
Merge pull request #27 from gina-alaska/add-annual-mod-monthly

Add annual mod monthly