give clearer names to the "create a directory" buttons

[zooko]

I watched someone (Dan Shoutis) use Tahoe-LAFS for the first time, using the WUI, and he was uncertain/confused about whether a created directory would be linked to from an extant directory or not. Currently there are two buttons in the WUI to create a directory. The one on the Welcome Page is labelled like:

• label: "Create a directory"
• button: "Create a directory"

and the one on the directory page is labelled like:

• label: "Create a new directory in this directory"
• label: "New directory name: " [text entry field]
• button: "Create"

Let's change this so that the Welcome Page has:

• button: "create an unlinked directory"

and the directory page has:

• label: "create a directory and link to it from this directory"
• label: "new directory name:" [text entry field]
• button: "create"

Opinions?

(By the way I deliberately changed capitalization because sentences should start with a capital letter and end with a punctuation mark and sentence fragments should do neither.)