#2 generic pattern for scan

[Murali Krishnan]

Besides suffixes and "all text files", allow file selection be a generic regular expression.

One example of where this would be useful would be to find multiple instances of "build.xml" in a directory structure.

This should be implemented in both the GUI and cmd line invocation.

The GUI may need context info explaining how to enter it.

This feature should be documented on the site.