Bug 425893

SUMMARY
When viewing large files in Kate, I want to filter the lines to reduce visible lines.

STEPS TO REPRODUCE
1. Examine large but noisy logs, e.g. /var/log/messages
2. On the command line, grep allows logs to be filtered.
3. I want a way to filter matching or non-matching lines in Kate.

OBSERVED RESULT
Kate includes a "Find" facility (CTRL+F).  However it lacks the ability to hide non-matching text.

EXPECTED RESULT
Extend the "power search and replace bar" to include three choices:
* No filtering (the current behaviour)
* Show matching lines
* Hide matching lines

Since the "Find" expression already supports regular expression mode, the user has lots of flexibility in deciding what to show/hide.  Hidden lines are still in the document, the hide/show steps don't modify the text of the document.

ADDITIONAL INFORMATION
The ability to filter large unstructured files provides benefit similar to code folding for source code, e.g. C++.  Wireshark's "display filters" provide a similar concept, though in quite a different context.