SOILWAT2 on devel branch preparing for major release v7.0.0

- SOILWAT2 will soon get a major new release with several improvements and new features
* milestone: https://github.com/DrylandEcology/SOILWAT2/milestone/13
* PR: DrylandEcology/SOILWAT2#325

- the purpose of this STEPWAT2 branch is to track progress in SOILWAT2 towards that major release and add any necessary changes to the STEPWAT2/SOILWAT2 interface
* one of the goals is to limit code changes required in STEPWAT2 and to reproduce previous STEPWAT2 behavior and output (new settings will be set such that they reproduce previous behavior)

- as of now, this commit pulls in SOILWAT2 commit ac323024c142840211c6e41d84083e7f4211ef3b (Merge pull request #324 from DrylandEcology/feature_soildensity_type)
* see PR: DrylandEcology/SOILWAT2#324
* new behavior: user specifies whether input soil density represents matric or bulk density (new input in `siteparam.in` with backwards compatible value of 0 = matric)
* this commit produces identical STEPWAT2 output as the current "master" (2022-June-17) on commit 69486d5

.gitmodules

@@ -1,5 +1,5 @@
 [submodule "sw_src"]
 	path = sw_src
 	url = https://github.com/DrylandEcology/SOILWAT2.git
-	branch = master
+	branch = release/devel_v7.0.0
         ignore = dirty

testing.sagebrush.master/Stepwat_Inputs/Input/sxw/Input/siteparam.in

@@ -73,6 +73,10 @@
 # Scenario
 RCP85
 
+# --- Soil characterization ---
+# Are inputs of density representing bulk soil (type 1) or the matric component (type 0)?
+0
+
 # ---- Transpiration regions ----
 # ndx  : 1=shallow, 2=medium, 3=deep, 4=very deep
 # layer: deepest layer number of the region.