ENH: Added a version support for finding ParaView.

A ParaViewConfigVersion.cmake is installed in the build directory, and
alongside the installed config file, allowing for calls such as
find_package(ParaView 3.8.0) to be used in CMakeLists files.

CMakeLists.txt

@@ -348,6 +348,11 @@ CONFIGURE_FILE(
     ${ParaView_SOURCE_DIR}/ParaViewConfig.cmake.in
     ${ParaView_BINARY_DIR}/ParaViewConfig.cmake 
     @ONLY IMMEDIATE)
+
+CONFIGURE_FILE(
+    ${ParaView_SOURCE_DIR}/ParaViewConfigVersion.cmake.in
+    ${ParaView_BINARY_DIR}/ParaViewConfigVersion.cmake
+    @ONLY IMMEDIATE)
     
 # used by the ParaViewConfig file to determine where the parts of the tree are located relative to the ParaViewConfig file.
 set(REL_REF "")
@@ -451,15 +456,16 @@ IF (NOT PV_INSTALL_NO_DEVELOPMENT)
   IF(WIN32)
     INSTALL(
         FILES "${BUILD_TREE}/CMake/tmp/ParaViewConfig.cmake"
+          "${BUILD_TREE}/ParaViewConfigVersion.cmake"
         DESTINATION .
         COMPONENT Development)
   ELSE(WIN32)
     INSTALL(
         FILES "${BUILD_TREE}/CMake/tmp/ParaViewConfig.cmake"
+          "${BUILD_TREE}/ParaViewConfigVersion.cmake"
         DESTINATION ${PV_INSTALL_LIB_DIR}
         COMPONENT Development)
   ENDIF(WIN32)
 
 ENDIF (NOT PV_INSTALL_NO_DEVELOPMENT)
 
-

ParaViewConfigVersion.cmake.in

+set(PACKAGE_VERSION @PARAVIEW_VERSION_MAJOR@.@PARAVIEW_VERSION_MINOR@.@PARAVIEW_VERSION_PATCH@)
+
+if("${PACKAGE_VERSION}" VERSION_LESS "${PACKAGE_FIND_VERSION}")
+  set(PACKAGE_VERSION_COMPATIBLE FALSE)
+else()
+  set(PACKAGE_VERSION_COMPATIBLE TRUE)
+  if ("${PACKAGE_VERSION}" STREQUAL "${PACKAGE_FIND_VERSION}")
+    set(PACKAGE_VERSION_EXACT TRUE)
+  endif()
+endif()