Separates general purpose functions into functions.mk
Adds 'make candy' to get makefile version infos
Adds forgotten .PHONY: set in build.mk
Implements mkrepo_load_param loading a param from the .mkrepo if undefined
Implements mkrepo_fetch_param returning a parameter's value in the repo
Implements mkrepo_save_param to get shell code saving a parameter
Moves the update rule at the very top
Implements 'make params' to show current .mkrepo parameters