Updates C++ and some unit tests

Author: StephenNneji

RATapi/examples/absorption/absorption.py

@@ -9,7 +9,7 @@ def absorption():
     """Custom layers model including absorption"""
     problem = RAT.Project(
         name="Absorption example",
-        calculation="non polarised",
+        calculation="normal",
         model="custom layers",
         geometry="substrate/liquid",
         absorption=True,

RATapi/examples/languages/setup_problem.py

@@ -38,7 +38,7 @@ def make_example_problem():
     # and H2O. Load these datafiles in and put them in the data block
 
     # Read in the datafiles
-    data_path = pathlib.Path("../data")
+    data_path = pathlib.Path(__file__).parents[1] / "data"
     D2O_data = np.loadtxt(data_path / "c_PLP0016596.dat", delimiter=",")
     SMW_data = np.loadtxt(data_path / "c_PLP0016601.dat", delimiter=",")
     H2O_data = np.loadtxt(data_path / "c_PLP0016607.dat", delimiter=",")