implementation of depth step fits

doc/examples/DepthProfiles/data/libGapIntegrals-test.dat

@@ -0,0 +1,36 @@
+# libGapIntegrals-test.dat
+# This is a comment
+% This as well
+header
+TITLE: Test superconductor data
+X-AXIS-TITLE: T (K)
+Y-AXIS-TITLE: #lambda^{-2} (#mum^{-2})
+SETUP: H #parallel c
+FIELD: 100
+TEMP: 0.0
+ENERGY: 4200
+# here the data will follow
+data
+# x, y, error y
+0.0318411, 7.77455, 0.2
+0.0629929, 7.9869, 0.15
+0.113914, 7.64209, 0.15
+0.202492, 7.37699, 0.15
+0.302725, 7.70893, 0.12
+0.447456, 7.77565, 0.12
+0.611685, 7.45768, 0.12
+0.813613, 7.19287, 0.12
+1.00822, 7.57813, 0.12
+1.24793, 7.31343, 0.12
+1.50635, 7.16818, 0.12
+1.74591, 6.99634, 0.12
+1.99795, 6.90414, 0.12
+2.25061, 6.41393, 0.12
+2.4958, 6.66666, 0.12
+2.75514, 5.93766, 0.12
+3.00753, 5.61992, 0.12
+3.26056, 4.89091, 0.12
+3.49414, 4.52005, 0.08
+3.75356, 3.73799, 0.08
+3.99425, 2.84974, 0.08
+4.30518, 1.35139, 0.08