Style improvements for component buttons
Allow component buttons code to be reused

method 'buttons' added to Component, so any inheriting class can override this method to return a list of required buttons that should go above the actual Component content
method 'content_buttons' added to Component (not used in sub classes, but can be overridden in plugins to customise these buttons)
export related stuff moved to TextSequence
blast stuff moved to tools plugins
Export stuff for TextSequence

buttons method added to TextSequence to serve for all child classes
export_type replace with export_options, and can be used to specify multiple options instead of just type (like caption, params)
export_type method changed to export_options

new Package to Package->new