ENH: add the module part to support external OpenJPEG

Modules/ThirdParty/OpenJPEG/CMakeLists.txt

 project(OTBOpenJPEG)
-set(OTBOpenJPEG_THIRD_PARTY 1)
-
-set(OTBOpenJPEG_LIBRARIES otbopenjpeg)
-set(OTBOpenJPEG_INCLUDE_DIRS
-  ${OTBOpenJPEG_BINARY_DIR}/src
-  )
-
-otb_module_impl()
+  
+  set(OTBOpenJPEG_SYSTEM_INCLUDE_DIRS ${OPENJPEG_INCLUDE_DIRS})
+  set(OTBOpenJPEG_LIBRARIES "${OPENJPEG_LIBRARIES}")
+  
+  otb_module_impl()

Modules/ThirdParty/OpenJPEG/otb-module-init.cmake

+find_package(OpenJPEG 
+  2.0.0
+  )

Modules/ThirdParty/OpenJPEG/otb-module.cmake

-set(DOCUMENTATION "This module provides OpenJPEG")
+set(DOCUMENTATION "This module imports OpenJPEG to the build system")
 
 otb_module(OTBOpenJPEG
+  DEPENDS
+  
+  TEST_DEPENDS
+  
   DESCRIPTION
     "${DOCUMENTATION}"
-  )
+)
 
 otb_module_activation_option("Enable OpenJpeg dependent modules. Note that this may not be needed if your GDal has a JPEG2000 compatible driver (other than jasper)" ON)