SUBMODULE: add data-community plugin (fixes #3146)

SUBMODULE: update turbulence-community plugin

ENH: README: add info to differentiate the modules from the plugins

.gitmodules

@@ -20,3 +20,6 @@
 [submodule "turbulence-community"]
 	path = plugins/turbulence-community
 	url = https://gitlab.com/openfoam/community/tc-turbulence/turbulence-community.git
+[submodule "plugins/data-community"]
+	path = plugins/data-community
+	url = https://gitlab.com/openfoam/community/sig-data-modelling/data-community.git

modules/README.md

 [[_TOC_]]
 
-## OpenFOAM Modules
+## OpenFOAM modules
 
 This directory is a location for additional OpenFOAM components or
 tools to placed and have them built as part of the normal OpenFOAM
 build process. It is assumed that each subdirectory contain an
 appropriate `Allwmake` (or `Allwmake.override`) file.
 
+The primary distinction between `modules` and `plugins` is that `modules` are
+mainly maintained and released by OpenFOAM developers, whereas `plugins` are an
+open and welcoming area for add-ons, predominantly maintained and driven by
+OpenFOAM community members and groups.
+
 ### How to use
 
 On the first use, you need to register the submodules, and then update them.
@@ -91,7 +96,7 @@ To build the doxygen information for the components, it is also
 necessary to link the directories to the doc/ subdirectory.
 This is a purely manual operation.
 
-### Developer Information
+### Developer information
 
 #### Build locations
 

plugins/README.md

 [[_TOC_]]
 
-## OpenFOAM Plugins
+## OpenFOAM plugins
 
 This directory is a location for additional OpenFOAM components or
 tools to placed and have them built as part of the normal OpenFOAM
 build process. It is assumed that each subdirectory contain an
 appropriate `Allwmake` (or `Allwmake.override`) file.
 
+The primary distinction between `modules` and `plugins` is that `modules` are
+mainly maintained and released by OpenFOAM developers, whereas `plugins` are an
+open and welcoming area for add-ons, predominantly maintained and driven by
+OpenFOAM community members and groups.
+
 ### How to use
 
 On the first use, you need to register the submodules, and then update them.
@@ -88,7 +93,7 @@ To build the doxygen information for the components, it is also
 necessary to link the directories to the doc/ subdirectory.
 This is a purely manual operation.
 
-### Developer Information
+### Developer information
 
 #### Build locations
 

data-community @ cfb50e6b

+Subproject commit cfb50e6b1a182bda5f25d5690f26a23fc8d22c8f

turbulence-community @ 4dbaff2c

-Subproject commit 06b391bb475f0386342b6f9b7fe5496ae87e464f
+Subproject commit 4dbaff2c56cacd3b5170cfd2899f003b1dc5832a