Create global default placement location

This means that `PlacementLocation.userLocal` should be hardcoded almost nowhere, but now the `--system` and `--local` arguments work on any command that requires fetching.

You can also see [here]() I fixed a bug that caused `/` to be added to the beginning of absolute paths beginning with drive letters on windows.

Also, sorry about the whitespace diffs, my text editor removes all trailing whitespace on save, and sometimes I miss some of them when committing.