App remembers the last directory accessed.
App remembers the last window size and position.
Fixed a bug in context menu when deleting removing all the graphs.
Added settings action to toolbar (not complete yet)
Added horizantal and vertical scroll bars, changed the layout.
Added the settings button to the toolbar, with image.
Added a SettingsPage class for settings page
Add/remove graphs using setting page.
Synced setting page options with context menu (not complete)
updated project file.