Default value of select editable (Issue #40)

in_array() returns true, when $needle is in array as value, but also when it is in array as key
This fix ensure correct default value of SelectBox in NiftyGrid editable - if value in table exist as a key,
is used this option, only if doesnt exist as a key, is used option with this as a value.
https://github.com/Niftyx/NiftyGrid/issues/40