Chainsaw: new setting to disable safe cutting

Some trees might generate with param2 != 0, which makes the
chainsaw appear blunt/useless. This safety feature is now
customizable.

settingtypes.txt

@@ -0,0 +1,9 @@
+#    Safety feature for the chainsaw tool aimed to prevent cutting structures
+#    built by players.
+#
+#    Trunk nodes generated by mapgen have a rotation of '0' whereas manually
+#    placed trunks usually have another value. However, some mods might generate
+#    trees with rotation != 0, which renders the chainsaw useless on them.
+#
+#    Disabling this feature will sacrifice safety for convenience.
+technic_safe_chainsaw (Chainsaw safety feature) bool true