description regex replace

[burrbull]

No description provided.

[burrbull]

cc @Emilgardis @adamgreig

The idea is to make it possible to use regex replacement in names and descriptions during modifying in addition to simple string assignment.
There are options how it can look like:

1. Add new _replace command with syntax similar to _modify. (more verbose, but little more flexible)
2. Do it during _modify. Use replace instead of assigment when pattern: replacer hashmap is passed instead of ordinary string. (like now in PR)
3. Some other variant?

What do you think?