Description of problem:
The project-wide search does not show results for search terms, if these are a substring of a longer word.

How reproducible:
always

Steps to Reproduce:
1. Open project-wide search
2. Search for the term "exampl" 

Actual results:
Messages containing the word "example" will not be shown in search results

Expected results:
Messages containing the word "example" should be shown in search results

Additional info:
The simple search within a document behaves as expected.
It is important to have the expected behaviour: to be able to find words using a substring, because in some languages words can have all sorts of different endings due to conjugation/declination.