Rename overloaded operators (add underscores)

* add suffix unary operators
* add _! operator
* _._ and _&_ operator overloading
* allow calling function references with _! and access variables with _._
* rename . method operator to !
* various cleaning & improvements

Documentation will follow at some point.

test/tests/function reference chain call.lua

@@ -0,0 +1,30 @@
+local _={}
+_[13]={}
+_[12]={}
+_[11]={}
+_[10]={text="3",tags=_[13]}
+_[9]={text="3",tags=_[12]}
+_[8]={text="1",tags=_[11]}
+_[7]={_[10]}
+_[6]={_[9]}
+_[5]={_[8]}
+_[4]={"return"}
+_[3]={"text",_[7]}
+_[2]={"text",_[6]}
+_[1]={"text",_[5]}
+return {_[1],_[2],_[3],_[4]}
+--[[
+{ "text", { {
+      tags = {},
+      text = "1"
+    } } }
+{ "text", { {
+      tags = {},
+      text = "3"
+    } } }
+{ "text", { {
+      tags = {},
+      text = "3"
+    } } }
+{ "return" }
+]]--