USER-DPD: Several updates to *_rx files: 1) Added MY_EPSILON to handle machine precision checks 2) Removed error checks for DPD-RX; enabled use with DPD-E simulations 3) Expanded the EOS functional form to allow corrections in the thermo file or on the command line 4) Updated naming convention from fraction to mixWtSite* 5) Changed the name of getParams() method to getMixingWeights() 6) getMixingWeights() now handles fractional and molecular weighting 7) Added optional argument (fractional or molecular) to pair_style command 8) Added argument to specify the exp6 parameter scaling method NOTE: Requires additional arguments in the pair coefficients, thus command line areguments are NOT backward-compatible.