Move RBC tutorial inside IncNavierStokes directory to fix packaging.

CMakeLists.txt

incns/CMakeLists.txt

incns/rbc/CMakeLists.txt

incns/rbc/img/RBC_2D_Solution.png

incns/rbc/img/eig_0.png

incns/rbc/img/plot.pdf

incns/rbc/img/rbc_geo.pdf

incns/rbc/rbc.tex

incns/rbc/rbc/completed/DNS/Ra_1e4_Pr0p71/dT_dy.fld

incns/rbc/rbc/completed/DNS/Ra_1e4_Pr0p71/dT_dy_bnd_b0.fld

incns/rbc/rbc/completed/DNS/Ra_1e4_Pr0p71/rbc-DNS.fld

incns/rbc/rbc/completed/DNS/Ra_1e4_Pr0p71/rbc-DNS.xml

incns/rbc/rbc/completed/DNS/Ra_1e4_Pr0p71/rbc.his

incns/rbc/rbc/completed/DNS/Ra_3e3_Pr_7/dT_dy.fld

incns/rbc/rbc/completed/DNS/Ra_3e3_Pr_7/dT_dy_bnd_b0.fld

incns/rbc/rbc/completed/DNS/Ra_3e3_Pr_7/rbc-DNS.fld

incns/rbc/rbc/completed/DNS/Ra_3e3_Pr_7/rbc-DNS.xml

incns/rbc/rbc/completed/DNS/Ra_3e3_Pr_7/rbc.his

incns/rbc/rbc/completed/DNS/Ra_5e3_Pr0p71/dT_dy.fld

incns/rbc/rbc/completed/DNS/Ra_5e3_Pr0p71/dT_dy_bnd_b0.fld