[UX] Add a "Login" link to the User Account menu and remove the login block from the sidebar

[quicksketch]

After adding the hero and new home page layout that is a single column (#1042), the out-of-box (prior to Basis theme) looks like this:

Aside from the "holy unfriendliness!" impression, I'm struck by the lack of the explanation how to log into the site. If I were a new user to Backdrop, I would have no idea how to log in. Oddly we still include the user login block in the default layout, so if I were to navigate to any other page, I would see a login option. However, from this screenshot you can see that there are NO links on the whole page! So there is nowhere to go to attempt a login in the first place.

So, proposal:

• Add "Login" to the User Account menu, which will make the link show up in the upper right corner.
• Remove the "Login" block from the default layout, as A) most sites don't have public login anyway and shoving it end-user's faces is weird and B) If we don't have the login box on the homepage it shouldn't be on secondary pages.

[bd0bd]

Happy to see right changes.
Thank you!

[quicksketch]

Great, lots of agreement here so I'll put this together.

As @jenlampton brought up to me, we're going to have an issue that our menu links don't have the ability to redirect back to the page you came from. So this means for now at least, clicking login will actually take you away from the page.

As an alternative, we could actually make the login link open a dialog (via AJAX) with the login form inside of it. But how we would enable/disable that option isn't figured out at this point.

[quicksketch]

PR filed at backdrop/backdrop#1546. Really simple approach here: Just manually add the link to the account menu on new installs.

[quicksketch]

Now with login link:

[quicksketch]

Merged backdrop/backdrop#1546 into 1.x for 1.5.0. No more login block!