Allow search by filename

[gnodar01]

As an extension to #38, it would be great to be able to search by filename.

The problem I'm personally having is that I have an application which has a Module abstract class that requires all concrete inheriting classes to define a run function. The issue is that I have many such concrete classes that get run in a pipeline fashion together. So I'll have dozens of occurrences of the run function show up in the sandwich view (which I can search for), and when I hover over any of them it will display the filename, e.g. src/modules/someconcretemodule::run and src/modules/someotherconcretemodule::run, but I can't search for "src/modules/someconcretemodule" specifically. Instead I have to go through the many occurrences of run until I find the one I'm looking for.

The general motivation is similar, it is often the case that the same function name appears many times throughout the codebase, but in different file. Being able to filter/search by function name AND filename, or just filename alone, would be very helpful.

[gnodar01]

Screenshot for an example of what I mean. It would be tremendously helpful to be able to search for measurecolocalization.py specifically