Optimized search fields from m2o

When searches from fields m2o 
![1](https://cloud.githubusercontent.com/assets/3594639/3033099/13afaf62-e060-11e3-9059-49467ad4e6de.png)
and have specified in xml "options = '{" no_create ": True}", and no matching results, in the form view not shown anything to the user, then this leaves the user confused.
![2](https://cloud.githubusercontent.com/assets/3594639/3033081/cceb8902-e05f-11e3-9746-dbf238c88da2.png)

I propose that when there are no results to display under field displays a message that says "No results to show".  Then the user will know what happened.
![3](https://cloud.githubusercontent.com/assets/3594639/3033085/e741ac78-e05f-11e3-9757-4ea0259a3db6.png)