Add test for depth method begin at end segment.

tests/app/depth_method_slab_begin_at_end_segment.dat

@@ -0,0 +1,4 @@
+549100 1.62751e+6 0 549100 10
+5.5555e6 1.64208e+6 0 575225 10
+5.55037e+6 1.63356e+6 0 585225 10
+5.5555e6 1.64208e+6 0 595225 10

tests/app/depth_method_slab_begin_at_end_segment.wb

@@ -0,0 +1,21 @@
+{
+  "version":"0.5",
+  "coordinate system":{"model":"spherical","depth method":"begin at end segment"},
+  "cross section":[[0,0],[45,0]],"surface temperature":273, "force surface temperature":true,
+  "potential mantle temperature":1673, "thermal expansion coefficient":3.1e-5,
+  "specific heat":1250, "thermal diffusivity":1.0e-6,
+  "features":
+  [
+    { "model":"subducting plate", "name":"Slab",
+     "coordinates":[[25,-5],[25,5]],
+     "interpolation":"continuous monotone spline",
+     "dip point":[0,0],
+          "segments":[{"length":200e3,"thickness":[300e3], "top truncation":[-300e3], "angle":[0,30]},
+          {"length":100e3, "thickness":[300e3], "top truncation":[-300e3], "angle":[30,50]},
+          {"length":800e3, "thickness":[300e3], "top truncation":[-200e3], "angle":[50,50]},
+          {"length":300e3, "thickness":[300e3], "top truncation":[-200e3], "angle":[50,10]},
+          {"length":300e3, "thickness":[300e3], "top truncation":[-300e3], "angle":[10,50]}],
+         "temperature models":[{"model":"uniform", "min distance slab top":-200e3, "temperature":900}]
+         }
+  ]
+}

tests/app/depth_method_slab_begin_at_end_segment/screen-output.log

@@ -0,0 +1,5 @@
+# x y z d g T 
+549100 1.62751e+6 0 549100 10 1917.06 
+5.5555e6 1.64208e+6 0 575225 10 900 
+5.55037e+6 1.63356e+6 0 585225 10 900 
+5.5555e6 1.64208e+6 0 595225 10 900