WIP: kMatrix for K1

[phdargen]

Added lineshape modifier to GenericKmatrix to control which channel is returned.
Works like this:

// Returns F_0 = (1-i K_0i) P_i
K(1)(1270)+[GenericKmatrix.channel.1]{rho(770)0{pi+,pi-},K+} 2 1.0 0.000 2 0.0 0.01
// Returns F_1= (1-i K_1i) P_i
K(1)(1270)+[GenericKmatrix.channel.2]{K*(892)0{K+,pi-},pi+} 2 1. 0.0001 2 0.0 0.01

K(1)(1270)+::kMatrix::channels {
K(1)(1270)+[phsp=WollyCusp]{rho(770)0{pi+,pi-},K+}
K(1)(1270)+[phsp=WollyCusp]{K*(892)0{K+,pi-},pi+}
}

If nothing is specified, the first channel is returned (as was previously the case).
Added additional K-matrix and P-vector definitions and 3-body phasespace approximation.
All changes should be backwards compatible.
Remaining issue is to figure out where to include barrier factors and how to normalise them.