implemented Clrf Instruction (#16)

Co-authored-by: darkress <30271678+DarkressX@users.noreply.github.com>
Reviewed-on: darkress/pic16f84-sim#16

de/darkress/pic16f84sim/commands/Clrf.java

@@ -0,0 +1,27 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Clrf extends FileRegisterCommandUtils implements Command
+{
+    private final int address;
+    private final boolean destinationBit;
+
+    public Clrf(int input)
+    {
+        address = input & 0x007F;
+        destinationBit = true;
+    }
+
+    @Override
+    public void execute()
+    {
+        final int result = 0;
+
+        checkZeroBit(result);
+
+        writeToDestination(destinationBit, address, result);
+        ProgramCounter.incPC();
+    }
+}