Resolve "FEATURE: Use time stamp from kurisu in update process"

Closes #109 (closed)

• New way of updating the db by re-using fileds when possible
• Check with the repo_timestamp in the repo module instead of getting the file's mtime
• Default the repo_timestamp to the file's mtime at upgrade time

CMakeLists.txt

@@ -66,6 +66,8 @@ set(Clang_C_FLAGS
     -Wno-format-nonliteral
     -Wno-missing-variable-declarations
     -Wno-unknown-warning-option
+    -Wno-declaration-after-statement
+    -Wno-double-promotion # Because of SDL2...
     -fcolor-diagnostics
 )
 set(Clang_CXX_FLAGS