Add Account and Folder models, update CMakeLists.txt with source files, add MailItem implementation

CMakeLists.txt

@@ -17,9 +17,12 @@ include_directories(${PROJECT_SOURCE_DIR}/src)
 
 # Source files - we will add them later
 set(SRC_FILES
+    src/main.cpp
     src/core/translator.cpp
-    src/services/synchronizer.cpp
-    # placeholder
+    src/core/mailitem.cpp
+    src/core/models/account.cpp
+    src/core/models/folder.cpp
+    # src/services/synchronizer.cpp  # placeholder
 )
 
 # Executable