entry.rs: Add documentation

libimagstore/src/entry.rs

@@ -2,6 +2,11 @@ use header::EntryHeader;
 use content::EntryContent;
 use store::StoreId;
 
+/**
+ * An Entry of the store
+ *
+ * Contains location, header and content part.
+ */
 #[derive(Debug, Clone)]
 pub struct Entry {
     location: StoreId,