add filter option

[elisunger]

No description provided.

[ermshiperete]

Looks good in general. A few comments and suggestions. I also found two scenarios where things don't yet work quite correct.

Also, can you please mention the issue number (#48) in the commit message.

The bottom three items of the ToDo list in #48 are still missing.

[ermshiperete]

We're getting closer! Thanks!

A few small nit-picks. Feel free to use GitHub's "Commit suggestion" or "Add suggestion to batch" feature if you like.

SIL.ReleaseTasks.md needs a bit more work. It was probably not clear what I meant when I asked to update the documentation; I hope it's clearer now.

Also, can you please add a line to the Unreleased section of CHANGELOG.md, something like:

## [Unreleased]

### Added

- [SIL.ReleaseTasks] Added filter option for project-specific entries (#48)

### Fixed
...

[ermshiperete]

lgtm