v0.8.1-alpha — the remote pointer is drawn, automatic saving, rotated backups

The remote pointer is finally drawn

Hovering a window edge in the remote session showed no resize arrows, text no
I-beam, a drag in Explorer no feedback — the Mac arrow stayed an arrow over
everything. The desktop image never contains the cursor: the server sends its shape
separately and expects the client to draw it, and nothing here was listening.

The shape now arrives, gets premultiplied for CoreGraphics (without which the soft
edge of a cursor comes out as a bright halo) and becomes a real NSCursor. Its size
is divided by the display's backing scale, so it isn't drawn at double size on a
Retina screen. A server hiding the pointer uses a transparent cursor rather than
NSCursor.hide(), which is a global counter — one unbalanced call and the pointer
disappears app-wide.

Save changes automatically

Settings has an interval: off, 1, 2, 5, 10, 15 or 30 minutes, default 5. While a
configuration has unsaved changes it is written out on its own, so nothing stands
between you and losing an afternoon of edits except a dialog you have to read.

Skipped while a file is still locked behind its master password: those passwords are
encrypted with a passphrase the app hasn't been given, and nothing should touch such
a file unattended.

Backups are rotated, to a count you choose

Every save still copies the configuration into the backups folder first, and the
oldest copies past the count are now deleted — off, 5, 10, 20, 50 or 100, default 10.
Same shape as mRemoteNG on Windows, which keeps 10 by the same copy-then-prune rule.

With automatic saving on, the history reaches back roughly the count times the
interval, so raise it if you want more room.

Two deliberate differences from Windows. Turning it off only stops new copies and
leaves the existing ones alone — mRemoteNG deletes every backup in that case, which is
a lot to throw away for a toggled setting. And copies are now named after the file
being saved rather than a fixed confCons: several configurations can share one
folder, and a shared name let one document's rotation delete another's copies.
Deletion is matched strictly against that naming, so nothing else you keep in that
folder is ever a candidate.