added file_copy_default_if_not_present() and replace_var_value_in_script()

CHANGELOG.md

@@ -4,6 +4,9 @@
 + **CONFIG:** Changed `cbuild/default_tasks` to `@cbuild/default_tasks`
 + Moved most scripts to `include/`
 + Renamed default config to `./project.config.default`
++ Added functions:
+    + `file_copy_default_if_not_present()`
+    + `replace_var_value_in_script()`
 
 ## 2.2.4
 + *default config*: C standard changed to C99