Change Glib::Variant<uint64_t> to Glib::Variant<guint64>.

This is needed on OSX/x86_64 where one is a typedef to unsigned long and the
other to unsigned long long. Both are the same size, but they are still
considered different types for the purposes of template instantiation, so the
specialisations which are defined for Glib::Variant<guint64> are not found if
Glib::Variant<uint64_t> is used.
Reimplement file save using the srzip output module.

This should fix (part of) bug #451.
LogicSignal: Removed trailing whitespace
LogicSignal: Tidied populate_popup_form is_checked
LogicSignal: Replaced TRUE/FALSE with true/false
SigSession: Replaced do { } while(0) with { }
Signal: Added a reference to _session
SigSession: Renamed get_device to device
StoreSession: Removed commented code
.gitignore: Ignore vim .swo files
SigSession: Made _sr_session non-static
SigSession: Added DeviceManager accessor functions
LogicSignal: Ported triggers to new API

This fixes bugs #448 and #452.
View: Update view on capture state change
.gitignore: Ignore QtCreator generated files.
SamplingBar: Add Space as a shortcut to Run/Stop.
Update description for Trace::get_label_rect()
DecodeTrace: Turn row_height and text_height into class members
DecodeTrace: Refactor sample helpers and simplify method calls
Trace: Introduce hover_point_changed()