* src/ui/call-record-row.ui: Add menu, GtkPopover. Surround existing
  elements with GtkEventBox to capture longpress/rightclicks
* src/calls-call-record-row.c: Provide functions emiting "call-delete"
  signal, add widgets from ui file
* src/calls-record.c: Add "call-delete" signal
* src/calls-history-box.c: Add callback for "call-delete" signal
* src/calls-record-store.c: Add callback for "call-delete" signal
* src/util.c: Add convenience function calls_find_in_store for finding
  items in ListModel
* src/util.h: Add declaration of calls_find_in_store