Clarify multiple file search scope

[robdesbois]

It would be great to see clarification in search_and_replace/search_and_replace_files.rst on how the include and exclude patterns interact with each other, and what the pattern syntax is (if that's covered elsewhere in docs it could be linked to)

For example, the filter *.cpp,-ut_*.cpp includes files matching the exclude filter, so it's clearly not a left-to-right ordered filter sequence. Same if pattern order is reversed. Does the search filter support such usage in some other way?