Changed wxGridCellEditor::GetString to use %f instead of %g to match
the Renderer, otherwise it would truncate/round the value to
m_precision significant digits instead of m_precision digits after the
decimal point.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@16745 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775