Make member variable underscores a suffix instead of a prefix

This change is made because tokens prefixed with underscore are reserved.
Renamed C++ headers to .hpp
Upgraded cotire to 1.6.6
MainWindow: Include device/file name in window title

This fixes bug #244
SamplingBar: Reduced indentation in update_sample_count_selector
Check LIMIT_SAMPLES and SAMPLERATE are available to read before reading them

This fixes bug #487
TimeMarker: Fixed display of negative value in popup

This fixes bug #460
DecodeTrace: Don't attempt to hover if the trace hasn't been painted yet
SamplingBar: Added reference to MainWindow for run_stop
Session: Renamed pv::SigSession to Session
MainWindow: Handle device selection failure

This fixes bug #455
StoreSession: Fixed completion mechanism

This fixes bug #451
LogicSignal: Removed redundant calls to match_action
LogicSignal: Renamed action_match and match_action
LogicSignal: Refactored get_trigger_types
icons: Added trigger markers
LogicSignal: Added an icon cache
LogicSignal: Added trigger markers
Fix saving of channel names in .sr files.

This closes bug #490.
Minor whitespace fixes.