Update settings to 2.48. Closes #63

Please review in particular such changes as my addition of web links for plugins or 3rd party tools mentioned in the settings, e.g. the link for Stash. I don't know if it's welcomed or inappropriate to have such links.
"a file" implies that there could be others. IMHO it would be better if it were written this way: "The global settings are stored in *the* file called .gitconfig in the user directory."
When it was originally written, the term "a file" was probably used because the writer thought about the many other files in the user directory. If you omit some of the sentence then "a file" is appropriate: "The global settings are stored in a file in the user directory."