TrackerCommand --> MeasureCommand + fuse against exception in MeasureTool dtor + added DeleteMeasureCommand + moved the various concrete measuring tool-related classes to their pre-assigned file locations (everything was crammed into MeasureCommands.* files up to this commit) + added double-click handler to GuiAdapter (for TOA implementation of "delete measuring tool on double-click")

#pragma once

#if ORTHANC_ENABLE_WASM == 1
// https://emscripten.org/docs/optimizing/Optimizing-WebGL.html
#  define ORTHANC_STONE_OPENGL_SHADER_VERSION_DIRECTIVE "precision mediump float;\n"
#else
#  define ORTHANC_STONE_OPENGL_SHADER_VERSION_DIRECTIVE "#version 110\n"
#endif