Pull out column definitions into an enum

    This isn't perfect, but it's a bit more structured, and it will help
    with things to come.
Factor out a simplified SegmentController interface to simplify tests
Add Ocelot.showModelessDialog and switch FilterView to use it

    This wraps panels in a parented dialog, so they're not independent
    frames that need to be minimized individually.
Add ColumnSelector that can add/remove columns

    This also exposes the (non-functional) Edit Distance column.
Add an Edit Distance column
Dialog refactoring
Clicking a table row will now toggle the associated checkbox

    This applies to the Configure Columns & Filters dialogs.
Simplify layout of column selector
Additional dialog refactoring
Merge pull request #5 from tingley/columns

Configurable columns, and per-segment edit distance values