new layer signs

[stefanocudini]

• [x] remove all unnecessary imports from camlayer
• [x] clone from camlayer the new traffic signs layer, with namespace 'signs'
• [ ] mapping signs icons and texts https://github.com/openmove/odh-mentor-otp/blob/master/vms/signs/codes.json

[RajaOpenMove]

you can close this issue is completed

[RajaOpenMove]

layer added but have to talk about json format to increase effectiveness, now its a clone of webcam

[stefanocudini]

• [x] code refactoring rename overlay-signs in overlay-vms

[stefanocudini]

data format sample: https://github.com/openmove/odh-mentor-otp/blob/dev/journey/tests/vms/stations.json