0.7.70_20190606_ci111

Reduce c++ headers usage

Switch to new forward declaration helper (in commons/fwd.h) and style (ClassPtr instead of Class::ptr) in order to reduce header files inclusion.

This helps getting faster compilation (around 40% less time in Travis).

Commit message:

Reduce c++ headers usage (#83)

* Remove unused RecordingInformation::ptr #trigger_build

* Add helper for forward declaration.
Port a few classes (Frame in particular) to new FWD syntax

* ImageHandler::ptr -> ImageHandlerPtr

* ImageHandlers::ptr -> ImageHandlersPtr

* Forward declarations for SaveImages

* Forward declarations for Driver and Camera

* Histogram::ptr -> HistogramPtr #trigger_ci

* Fix ubuntu 16.04 build

* FileWriter::Ptr -> FileWriterPtr

* PlanetaryImager::Ptr -> PlanetaryImagerPtr

* DriverForwarder::ptr => DriverForwarderPtr

* FilesystemBrowser::ptr => FilesystemBrowserPtr

* QHYImagingWorker::Ptr -> QHYImagingWorkerPtr #trigger_ci

* RemoteDriver::ptr => RemoteDriverPtrRemoteDriver

* Split NetworkDispatcher and NetworkReceiver header/implementation
NetworkDispatcher::ptr => NetworkDispatcherPtr
#trigger_ci

* NetworkPacket::ptr => NetworkPacketPtr

* NetworkPacket::ptr => NetworkPacketPtr #trigger_ci

* RemoteFilesystem::ptr => RemoteFilesystemPtr

* NetworkClient::ptr => NetworkClientPtr

* SaveFileForwarder::ptr => SaveFileForwarderPtr

* Fix NetworkClientPtr

* FilesystemForwarder::ptr => FilesystemForwarderPtr

* V4L2Buffer::ptr => V4L2BufferPtr

* V4L2Device::ptr => V4L2DevicePtr

* V4L2Control::ptr => V4L2ControlPtr

* Fwd for V4L2 Formats and nested classes #trigger_ci

* QHYControl::ptr => QHYControlPtr

* ASIImagingWorker::ptr => ASIImagingWorkerPtr

* ROIValidator::ptr => ROIValidatorPtr

* More headers cleanup