Add configuration for own name of cursor

[isqad]

I'd like to assign my own name of cursor during declare. Here it is defined rigidly:

postgresql_cursor/lib/postgresql_cursor/cursor.rb

Line 180 in 4107487

@cursor = SecureRandom.uuid.gsub("-","")

[afair]

I added that capability in commit 3ba3253. Use the cursor_name: "myname" (which must be a valid cursor name. I am curious why you would need this? Perhaps tracing though the system.