Fixing getOne to not error on 0 results

Adding a simple isset to check if res[0] is actually set, if so return it if not return null so we don't have a floating result.

Added count variable which stores returned rows count

Some readme improvements

Allow to pass bind variables for func()

More real example of func

Calling reset should set values to null instead of unsetting them

Gets rid of multiple PHP warning messages

Added optional port parameter to change the default mysqli.default_port