Bugfix: perform residual color contractions before stripping group factors

Problem: when resolving a C factor multiplying a vertex in a
self-energy diagram, color-index-dependent group factors had been
stripped before the indices were contracted.  For instance, the result
from ResolveColorFactor[_, _, Cp[SOc, conj[SOc], conj[SOc], SOc], _],
needed for the sgluon self-energy, was

-2 I g3^2 sum[j1,1,8,fSU3[1,1,j1]^2]-I g3^2 (sum[j1,1,8,fSU3[1,2,j1]^2]+sum[j1,1,8,fSU3[1,1,j1] fSU3[2,2,j1]])-I g3^2 (sum[j1,1,8,fSU3[1,3,j1]^2]+sum[j1,1,8,fSU3[1,1,j1] fSU3[3,3,j1]])-I g3^2 (sum[j1,1,8,fSU3[1,4,j1]^2]+sum[j1,1,8,fSU3[1,1,j1] fSU3[4,4,j1]])-I g3^2 (sum[j1,1,8,fSU3[1,5,j1]^2]+sum[j1,1,8,fSU3[1,1,j1] fSU3[5,5,j1]])-I g3^2 (sum[j1,1,8,fSU3[1,6,j1]^2]+sum[j1,1,8,fSU3[1,1,j1] fSU3[6,6,j1]])-I g3^2 (sum[j1,1,8,fSU3[1,7,j1]^2]+sum[j1,1,8,fSU3[1,1,j1] fSU3[7,7,j1]])-I g3^2 (sum[j1,1,8,fSU3[1,8,j1]^2]+sum[j1,1,8,fSU3[1,1,j1] fSU3[8,8,j1]])

wherein summations over j1 were supposed to be performed before
stripping fSU3[]s.  However, this failed to take place, leading to the
wrong vertex value, -128*g3^2.  After the fix, the correct value,
-3*g3^2, is obtained.

From: Philip Diessner
Subject: Re: SARAH/SPheno/FlexibleSUSY: Color factors in octet self energy
Date: Wed, 08 Oct 2014 16:31:48 +0200

Dear all,

thanks for these fast fixes.
After using both new versions of the generators the couplings and
signs now agree with FA/FC and
both programs deliver the same value for the mass in the accuracy I
would expect.

As we are going now also through other sectors more carefully, it
might be that you hear back from us again ;)

Cheers
Philip and Wojciech
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