<b>File S1</b> contains appendices describing all analytical derivations and supplementary figures. <b>File S2</b> provides the details of the analytical derivations as a Mathematica^© source code (<i>MATHEMATICA v. 9.0 </i>Wolfram Research 2012). <b>File S3 </b>provides the simulation code also as a Mathematica^© source code (<i>MATHEMATICA v. 9.0 </i>Wolfram Research 2012).