Made filter addable and removable
Added short cuts to open file, quit and help
Added enter for committing when filtering
Added a way to search and replace content in rows.
Added unit tests for filtering text rows.
Added unit tests for regular expression filtering. + generalized unit tests
Started work on making the filter pane listen to the filters that are added or removed
Written code so that tabs can be closed in the document.
Added Copy to clipboard function to util.