Make further properties multi-client and thread-safe

Move MovingPrimary, MovingSecondary, EarliestNonSlewingTime to
SharedResources, make all new properties thread-safe (atomic)
operations.

Meade.net.UnitTests/ThreadSafeBoolTests.cs

@@ -0,0 +1,39 @@
+using ASCOM.Meade.net;
+using NUnit.Framework;
+
+namespace Meade.net.UnitTests
+{
+    public class ThreadSafeBoolTests
+    {
+        [TestCase(false)]
+        [TestCase(true)]
+        public void WhenConvertedValueIsSame(bool value)
+        {
+            // given
+            ThreadSafeBool sut = value;
+
+            // when
+            bool actual = sut;
+
+            // then
+            Assert.That(actual, Is.EqualTo(value));
+        }
+
+        [TestCase(false, false)]
+        [TestCase(false, true)]
+        [TestCase(true, false)]
+        [TestCase(true, true)]
+        public void WhenSetValueIsChanged(bool value, bool setValue)
+        {
+            // given
+            ThreadSafeBool sut = value;
+
+            // when
+            sut.Set(setValue);
+            bool afterset = sut;
+
+            // then
+            Assert.That(afterset, Is.EqualTo(setValue));
+        }
+    }
+}