Abandon possible addition of further collections & restructure repo

[delphidabbler]

After three years it's looking less likely that further snippet collections will be added to the repository, so it seems sensible to give up on the idea.

If the repository is to be repurposed for the DelphiDabbler Code Snippets collection then the separate csdb directory is no longer required. The content of that directory can therefore be moved up a level and the csdb directory can be deleted.

[delphidabbler]

Once this is done the releases can be renamed since there's no need to explicitly specify which collection the releases relate to.

[delphidabbler]

Implemented at merge commit 26ee70a