Inheriting from the Client's URI options is not implemented, as it depends on PHPC-196.

This commit also revises the documentation for selectDatabase(), selectCollection(), and the core class constructors.

This also changes the existing collection functional test to inherit FunctionTestCase

PHPC-224 consolidated the Result and Cursor classes into one. Additionally, PHPC-203 changed toArray() to return iterator_to_array($this) instead of only the first result document. For commands, this means we need to extract the first element in toArray()'s return value.