Flatten developer guide sections
Implement PrestoConnection.getTransactionIsolation

Resolves #2031
Fix ArrayIndexOutOfBoundsException when parsing Hive timestamp column
Simplify example code for isNull function
Require Java 8
Remove dependency on floatingdecimal library
Change TPCH dates to be DATE type

Fix date handling bugs in query tests, kafka tests, and jdbc connector
Map DATE to TEXT in Cassandra connector
Change DATE memory representation to be days

DATE is now stored as a 32-bit number of days since 1970-01-01