Shortening Database Design section and moving to beginning

Also moves Setup section to the very beginning
Minor tweaks to SQL lecture

1. Reordering date queries to year, month, day
2. Removing mass unit conversion from second problem
Tweak the sorting section of the SQL lecture

1. Initial sort example using taxa
2. Change exercise to focus on surveys table and include an expression
Add information on adding new data to tables

Plus lots of minor tweaks throughout
Merge remote-tracking branch 'origin/master'