Ani 2x (#480)

* Adding ANI-2x parameters

* Moving 2x to seperate branch

* Adding ANI-2x to new branch

* Adding 2x network

* Update models.py

* Update api.rst

* Update __init__.py
Co-authored-by: Christian Devereux <cdever01@ufl.edu>
Co-authored-by: Farhad Ramezanghorbani <farhadrgh@users.noreply.github.com>

torchani/resources/ani-2x_8x/train5/networks/ANN-O.nnf-l4.bparam

+
\ No newline at end of file

torchani/resources/ani-2x_8x/train5/networks/ANN-S.nnf-l4.bparam

+fs7
\ No newline at end of file

torchani/resources/ani-2x_8x/train5/networks/ANN-S.nnf-l4.wparam

+]6͖^XT67A7ivq=W˾2ʶ.x
?;4W74b6w鶇~K=6t6S$F68{6
~$pov.YB6#4?{7(#
ǂ#67|84"==)T=A,>p6RE튶Z]77=E6]ۖ
5\)նѶgdpOɡ6Ij{5~636.=t6F5p=626â	7ṙhUzW6NT=68A=J/\jDV<6 =U:*Y<@>Wr07m=6ga786j{47C%=
\ No newline at end of file

torchani/resources/ani-2x_8x/train5/rHCNOSFCl-5.1R_16-3.5A_a8-4.params

+DESC = ANI_NORMAL
+TM = 1
+CG = 0
+RP = 0
+AC = 0
+Rcr = 5.1000e+00
+Rca = 3.5000e+00
+EtaR = [1.9700000e+01]
+ShfR = [8.0000000e-01,1.0687500e+00,1.3375000e+00,1.6062500e+00,1.8750000e+00,2.1437500e+00,2.4125000e+00,2.6812500e+00,2.9500000e+00,3.2187500e+00,3.4875000e+00,3.7562500e+00,4.0250000e+00,4.2937500e+00,4.5625000e+00,4.8312500e+00]
+Zeta = [1.4100000e+01]
+ShfZ = [3.9269908e-01,1.1780972e+00,1.9634954e+00,2.7488936e+00]
+EtaA = [1.2500000e+01]
+ShfA = [8.0000000e-01,1.1375000e+00,1.4750000e+00,1.8125000e+00,2.1500000e+00,2.4875000e+00,2.8250000e+00,3.1625000e+00]
+Atyp = [H,C,N,O,S,F,Cl]

torchani/resources/ani-2x_8x/train5/sae_linfit.dat

+H,0=-0.5978583943827134
+C,1=-38.08933878049795
+N,2=-54.711968298621066
+O,3=-75.19106774742086
+S,4=-398.1577125334925
+F,5=-99.80348506781634
+Cl,6=-460.1681939421027