feat(ast): add species base to template declarations

Added optional species_base field to Template struct enabling
template-species inheritance syntax: `template Name: Species { ... }`.
Updated LALRPOP grammar and all Template construction sites.

src/syntax/ast.rs

@@ -138,6 +138,7 @@ pub struct Character {
 #[derive(Debug, Clone, PartialEq)]
 pub struct Template {
     pub name: String,
+    pub species_base: Option<String>, // `: Species` - type constraint from species
     pub fields: Vec<Field>,
     pub strict: bool,
     pub includes: Vec<String>,