fixed deleting of events
removed link to not available settings page
moved truncate function from admin_event_table class to db class
removed obsolete code lines
added and implemented shortcode attribute details_length
changed parameters from number to a more significant wording
adapted help text to changed parameter values
moved visibility check to function
implemented attribute values 'event_list_only' and 'single_event_only'
changed standard value for attribute 'link_to_event'
removed obsolete check
added compatibility to older versions for the widget
updated about screenshot
preparation for version 0.3.4
Merge branch 'develop'