Changed a few things

- Bumped to 0.15.0
- Add boot script
- Change variable definition syntax, using a = to distinguish more cleary between identifier and value
- Variables initial values are evaluated on first use instead of at parsing time
- Error on variable redefinition. Means you should make sure to load saves after your scripts.
- Improve string parsing, support for escape codes
- Remove support for number literals with empty decimal part (42. for 42.0) as there's no distinction in Anselme and it conflicts with .function call suffix
- Changed priority of : pair operator
- Add type type, and type annotations to variables and function parameters
- Change Lua function system to use regular Anselme functions
  - Defining a function from Lua is now way simpler and require providing a full Anselme function signature
- Change Anselme function system
  - Dynamic dispatch, based on arity, type annotation and parameter names. Will select the most specific function at runtime.
  - Define way to overload most operators
  - Allow custom type to text formatters
  - Allow assignment to custom functions
  - Index operator ( renamed to ()
  - Functions with parameters each have their own private namespace (scoping ersatz)
  - Internal: "custom"-mode operators now have their own expression AST type instead of cluttering the function system
- Remove static type checker as it is barely useful with new function system. May or may not rewrite one in the future.
- Improve error messages here and there
- Internal: cleaning

test/tests/function custom type dispatch.ans

@@ -0,0 +1,15 @@
+:name="name"::string
+:french name="french"::name
+:esperanto name="esperanto"::name
+
+$ a(name)
+	{name} is english or generic
+
+$ a(name:nom::french name)
+	{nom} is french
+
+~ a("bob"::name)
+
+~ a("pierre"::french name)
+
+~ a("idk"::esperanto name)