Abins thresholding: update system tests

System tests for Abins are modified to calculate up to second-order
excitations only (as third and fourth-order are currently disabled.)

In addition, the test data for two other tests needs updating;
BezeneBinWidthCASTEP and TolueneScale have small changes in the
results. This is associated with a more conservative criterion for
discarding small values compared to the previous system; results
similar to the previous setup can be obtained by modifying the
threshold used in
SPowderSemiEmpiricalCalculator._calculate_s_over_threshold

Testing/Data/SystemTest/BenzeneBinWidthCASTEP.nxs.md5

-8c4c9164cbd6256b8fe558a8cc5aab2f
+3927dcd4999b921628501dad08ff140d

Testing/Data/SystemTest/C6H5Cl-Gaussian.nxs.md5

-426766659eb52b2cdca5f4c452269af6
+2d0ba9a56ef63248031cc24fb2c10fe8

Testing/Data/SystemTest/Na2SiF6_CASTEP.nxs.md5

-6a9ebb184ce6cbad194d2f4217e8e6c2
+e6669ec5dd49fc7f2c835ba3a6ff707b

Testing/Data/SystemTest/Na2SiF6_DMOL3.nxs.md5

-23947afbbcec326052018f34551993a3
+6e851997cfba0cec009e307fa1c95031

Testing/Data/SystemTest/TolueneLargerOrderAbins.nxs.md5

-7031da500c989b8ee3b7e884ab12426c
+28ec7e6f3b4ff61f50d1eecdaf133471

Testing/Data/SystemTest/TolueneScale.nxs.md5

-d1a0e156844c6459d230763742e21080
+e40d2e8696fe8608beea25299e3007c0

Testing/Data/SystemTest/TolueneScratchAbins.nxs.md5

-ab23cd079e36f46dd610dc22a9d8beac
+c8a50f44d2b3300eb26e1a891c8c60fe

Testing/SystemTests/tests/analysis/AbinsTest.py

@@ -176,7 +176,7 @@ class AbinsCRYSTALTestScratch(systemtesting.MantidSystemTest, HelperTestingClass
         self.ref_result = name + ".nxs"
         self.set_ab_initio_program("CRYSTAL")
         self.set_name(name)
-        self.set_order(AbinsConstants.QUANTUM_ORDER_FOUR)
+        self.set_order(AbinsConstants.QUANTUM_ORDER_TWO)
         self.case_from_scratch()
 
     def excludeInPullRequests(self):
@@ -263,8 +263,8 @@ class AbinsCRYSTALTestLargerOrder(systemtesting.MantidSystemTest, HelperTestingC
         self.ref_result = name + ".nxs"
         self.set_ab_initio_program("CRYSTAL")
         self.set_name(name)
-        self.set_order(AbinsConstants.QUANTUM_ORDER_TWO)
-        self.case_restart_diff_order(AbinsConstants.QUANTUM_ORDER_THREE)
+        self.set_order(AbinsConstants.QUANTUM_ORDER_ONE)
+        self.case_restart_diff_order(AbinsConstants.QUANTUM_ORDER_TWO)
 
     def excludeInPullRequests(self):
         return True
@@ -343,7 +343,7 @@ class AbinsCASTEPNoH(systemtesting.MantidSystemTest, HelperTestingClass):
         self.ref_result = name + ".nxs"
         self.set_ab_initio_program("CASTEP")
         self.set_name(name)
-        self.set_order(AbinsConstants.QUANTUM_ORDER_FOUR)
+        self.set_order(AbinsConstants.QUANTUM_ORDER_TWO)
         self.set_cross_section(cross_section="Total")
         self.case_from_scratch()
         self._wrk_1 = self._output_name
@@ -394,7 +394,7 @@ class AbinsDMOL3TestScratch(systemtesting.MantidSystemTest, HelperTestingClass):
         self.ref_result = name + ".nxs"
         self.set_ab_initio_program("DMOL3")
         self.set_name(name)
-        self.set_order(AbinsConstants.QUANTUM_ORDER_FOUR)
+        self.set_order(AbinsConstants.QUANTUM_ORDER_TWO)
         self.set_cross_section(cross_section="Total")
         self.case_from_scratch()
 
@@ -422,7 +422,7 @@ class AbinsGAUSSIANestScratch(systemtesting.MantidSystemTest, HelperTestingClass
         self.ref_result = name + ".nxs"
         self.set_ab_initio_program("GAUSSIAN")
         self.set_name(name)
-        self.set_order(AbinsConstants.QUANTUM_ORDER_FOUR)
+        self.set_order(AbinsConstants.QUANTUM_ORDER_TWO)
         self.set_cross_section(cross_section="Incoherent")
         self.case_from_scratch()