Move framework modules into subfolder

[jimm-domingo]

Changing the directory structure would benefit developers of this framework as well as developers of toolkits that use the framework. Currently, framework and toolkit modules are all together in the same project folder. This makes it difficult to know which modules are framework-related versus toolkit-specific, especially with toolkit projects that have many non-framework modules.

To clearly distinguish between the two types of modules, the framework modules should be relocated into a subfolder. That would leave the toolkit-specific modules in the project's main folder, which makes sense since those are the ones that the toolkit developers edit.

So this is how the current modules in this project would be re-organized:

{project}/
  ├─ Simple Toolkit_DEV.xlam
  ├─ Simple Toolkit_conf.bas
  ├─ menu_defn_in_code.bas
  ├─ tools.bas
  └─ framework/
       ├─ Sheet1.cls
       ├─ ThisWorkbook.cls
       ├─ bootstrap.bas
       ├─ dev_tools.bas
       ├─ excel_ver.bas
       ├─ file_utils.bas
       ├─ loader.bas
       ├─ menu.bas
       ├─ menu_lib.bas
       ├─ toolkit.bas
       └─ update_core.bas