Find non-ascii characters in non-UTF8 files in "Find in Project"

In the 'Find in project' window, we were not able to find correctly in non-UTF8 even if the correct encoding was specified in the .tm_properties file. 

My commit try to use the information the the property file and convert on the fly the content of the file in UTF-8. Like this, we are not showing 'Binary file' on each file that is not in UTF-8 and we are able to find Non-ASCII characters in these files.