Fix bug #477 by keeping track of visible rows, not just titles
View: Added viewport() accessor method
DecodeTrace: Make tool tips use mapToGlobal() of the view's viewport
DecodeTrace: Simplified and reduced calls to View
Trace: Converted on_hover_point_changed signal to direct notification
DecodeTrace: Tidied up get_sample_range
DecodeTrace: Combined together get_pixels_offset with get_samples_per_pixel
Header: Fixed mouse over coordinates
Trace: Renamed get_label_rect to label_rect
Trace: Correct shape of label_rect
Trace: Removed pt_in_label_rect
View: Replace compare_trace_v_offsets with a lambda
View: Simplified get_traces
Replaced duplicated code with Trace::get_y
DecodeTrace: Removed set_view
Refactored common row functionality into RowItem
RowItem: Renamed get_v_offset to v_offset
Trace: Renamed get_name() to name()
Trace: Renamed get_colour() to colour()
Added RowItemOwner