Container name length limit option

[acahill]

As described in #26, this adds two minor features to work around an issue with the Container Name addon Long Names Word wrap are overlapping with other entries #2544:

1. Limit the length of a container name to a configurable max length. An option seemed like the way to go here, because the exact number of characters might change depending on the OS, browser theme, accessibility settings, etc.
2. Option to delete a common string like "MyCompany" from all container names. This helps if the unique part is at the end of the name

I used the name "slug" for that second option because it reminded me of slugs in URLs, but in this case it's deleting the least unique part of the name. Oh well, couldn't think of a better word for it.