Added 2 new CreateIndex() methods which take a string[] columnNames argument.

This is just a much much much cleaner way of providing an API that is meant
to index an array of columns in a table.

Also fixed the gross hack that CreateTable() was using in order to index
multiple columns by using the new API.
Merge pull request #232 from jstedfast/create-index-with-column-array

Added 2 new CreateIndex() methods which take a string[] columnNames argument