Track changes in default letters

[danmichaelo]

We need to track changes in the default letters. First plan was to use a different branch, but I think we have diverged so much from the default in some cases (e.g. by removing tables) that we cannot rely on regularly merging in changes, but rather will have to track the changes and do modifications as needed. We can keep the default letters in a separate folder and use some standard commit message for updates to the default letters.

The script to fetch the original letters will have to be slightly different, so we need a new command like pull default(?)

[danmichaelo]

Added in 6ae473bbe436724eaa381a05a4623cbba8ab09dd