ENH: add clearing capability in ImageKeywordlist (used in Monteverdi)

Code/IO/otbImageKeywordlist.cxx

@@ -83,6 +83,14 @@ GetMetadataByKey(const std::string& key) const
   // Then if everything is ok, return the ossinString
   return it->second;
 }
+
+void 
+ImageKeywordlist::
+ClearMetadataByKey(const std::string& key)
+{
+  m_Keywordlist[key] = "";
+}
+
 void
 ImageKeywordlist::
 convertToOSSIMKeywordlist(ossimKeywordlist& kwl) const

Code/IO/otbImageKeywordlist.h

@@ -74,6 +74,9 @@ public:
   /** Get the Data object descriptor corresponding to the given key */
   const std::string& GetMetadataByKey(const std::string& key) const;
 
+  /** Clear a given field of the keyword list */
+  virtual void ClearMetadataByKey(const std::string& key);
+
   virtual void convertToOSSIMKeywordlist(ossimKeywordlist& kwl) const;
 
   virtual void Print(std::ostream& os, itk::Indent indent = 0) const;