Meter for AeroQuad OSD to assist in monitoring landing

This module is an effort to create a meter for AeroQuad OSD to assist in monitoring landing speed
AeroQuad OSD meter to assist monitoring landing

void displayVariometer(byte flightMode) should be called in 50Hz slice
AeroQuad OSD meter to assist monitoring landing

#define ShowLandingIndicator in configuration.h
AeroQuad OSD meter to assist monitoring landing

added //#define ShowLandingIndicator
Merge pull request #389 from norem/development

Development