0025422: Visualization, TKOpenGl - support re-assignment of new window to existing View
Do not throw "Window already defined" exception in Visual3d_View/V3d_View.
Handle window change within OpenGl_GraphicDriver::View().
OpenGl_GraphicDriver - introduce dedicated methods to initialize/release shared OpenGL context.
::InitEglContext() to using existing EGL context.
OpenGl_Context - always enable NPOT textures on OpenGL ES 2.0
OpenGl_Workspace - do not call glDisable/glEnable(GL_TEXTURE_2D) on GL ES
OpenGl_GraphicDriver::ReleaseContext() - release EGL context on destruction
OpenGl_GraphicDriver::InitEglContext() - escape method implementation with HAVE_EGL macros
OpenGl_ShaderManager - clear shader programs on shared context invalidation