outshine-speed-commands-default: update to align with org equivalent

[Hugo-Heagren]

Fix #91. This is a draft PR because there were two problems raised in that issue and so far it only solves one of them -- consistency between the default speed command lists in org and outshine.

The other is that -- unlike org -- outshine inserts new headings above old ones when outshine-insert-heading is called with a speed command.

I found that this is because outshine only adds a newline for the new heading after the current one if point is not at BOL. If it is, it inserts the heading there with a trailing newline, pushing the old heading onto the next line. Of course, speed commands (like i) are invoked from BOL, so this always happens.

It's a very simple fix, just remove the unless statement and merge the newline creation into the main body of the function. But before I do that, I wanted to check why there is different behaviour for BOL at all? It seems such a strange exception that I thought it might be a protection for something specific that needs keeping. Basically, is there a good reason not to make the simple fix?