[mkgmap-dev] Reworked access tag handling

Hi, Prompted by Carlos' message, I have reworked the access tag handling. Also, I have removed the built-in handling of footpath, cycleway and bridleway and modified the lines style file to add the appropriate access tags. Also added access tags for steps. So, if you are using your own style files, please modify the lines file accordingly. Please report any breakage. Cheers, Mark