maint: move all classes to start of script
maint: rename add_default_section to AddDefaultSection
maint: move global variables after class declarations
maint: change function locations

Move remove_file_on_error, file_replace, file_rewrite functions
maint: sort import statements
maint: move all function declarations to start of script

(after class declarations)
maint: iniparse.DEFAULTSECT initialization moved to separate function
maint: move sys.excepthook initialization after all declarations
maint: add main() function
maint: change global variables location
maint: move top level logic to new crudini class