Update cases with mode-2 ISW

Combined the mapped and unmapped cases for this into a single
case file.

src/cases/mode2_ISW/spins.conf

+## Mode-2 ISW (density) configuration file
+
+# Spatial Parameters
+Lx = 6.4
+Ly = 1.0
+Lz = 0.30
+Nx = 4096
+Ny = 1
+Nz = 384
+min_x = 0
+min_y = 0
+min_z = 0
+
+# Expansion types
+type_x = FREE_SLIP
+type_y = FOURIER
+type_z = FREE_SLIP
+mapped_grid = false
+
+# Physical Parameters
+g = 9.81
+rot_f = 0.0e-3
+rho_0 = 1000.0
+visco = 2e-6
+kappa_rho = 2e-7
+kappa_tracer = 2e-7
+
+# Problem Parameters (delta_rho is percentage)
+delta_rho = 0.023
+pyc_asym = 0.0
+pyc_sep = 0.0
+h_halfwidth = 0.01
+h_mix_half = 0.01
+delta_x = 0.02
+Lmix = 0.30
+Hmix = 0.10
+dye_thickness = 0.01
+dye_halfwidth = 0.005
+enable_tracer = false
+
+# Problem topography parameters
+hill_height = 0.10
+hill_centre = 4.8
+hill_width = 0.10
+
+# Temporal Parameters
+final_time = 150
+plot_interval = 1
+#dt_max = 0.0
+
+# Restart Options
+restart = false
+restart_time = 0.0
+restart_sequence = 0
+restart_from_dump = false
+compute_time = -1
+
+# Perturbation Parameter
+perturb = 1e-3
+
+# Filter Parameters
+f_cutoff = 0.6
+f_order = 2.0
+f_strength = 20.0
+
+# secondary diagnostics
+#compute_enstrophy = true
+#compute_dissipation = true
+#compute_BPE = true
+#compute_internal_to_BPE = true
+#compute_stresses_top = false
+#compute_stresses_bottom = true

src/cases/tankrho/spins.conf

-restart = false
-Lx = 1.0
-Ly = 1.0
-Lz = 1.0
-Nx = 1024 
-Ny = 1
-Nz = 1024
-
-rho_0 = 1.0
-delta_rho = 0.01
-pyc_asym = 0.0
-pyc_sep_perc = 0.0
-h_perc =0.1
-h_mix_perc = 0.1
-delta_x = 0.01
-Lmix = 0.1
-Hmix = 0.1
-
-hill_height = 0.1
-hill_centre = 0.5
-hill_width  = 0.1
-
-visco = 0.0001
-diffu_rho = 0.00001
-
-plot_interval = 1.0
-final_time = 0.5
-
-perturb  = 0.0001
-