Merge pull request #1 from OHDSI/master

Update from original repo
Delete OMOPv4 to PCORnetv1 ETL Description 22-Sep-14.docx

We dont need a word document since we now have the markdown version
Update OMOPv4_to_PCORnetv1_ETL_Description.md

Made changes to the Encounter table description
Update OMOPv4_to_PCORnetv1_ETL_Description.md
Updated Encounter query (provider_id as NULL)
updating DIAGNOSIS table join
Merge pull request #6 from writetoritu/master

Update to documentation and Encounter query (provider_id) field