content: rename image to icon and assign one

content/tools/agora.md

 +++
 title = "Agora"
 date = 2018-09-01T02:56:19+02:00
-image = ""
+icon = "conversation"
 color = "#ABB7B7"
 alt = ""
 link1 = "https://agora.degrowth.net"

content/tools/calendars.md

 +++
 title = "Calendars"
 date = 2018-09-01T07:56:19+02:00
-image = ""
+icon = "calendar"
 alt = ""
 color = "#ABB7B7"
 link1 = "https://cloud.degrowth.net/"

content/tools/calls.md

 +++
 title = "Calls"
 date = 2018-09-01T09:56:20+02:00
-image = ""
+icon = "teleconference"
 alt = ""
 color = ""
 link1 = ""

content/tools/chat.md

 +++
 title = "Chat"
 date = 2018-09-01T01:53:12+02:00
-image = ""
+icon = "exchange"
 alt = ""
 color = ""
 link1 = ""

content/tools/events.md

 +++
 title = "Events"
 date = 2018-09-01T06:56:19+02:00
-image = ""
+icon = "event"
 alt = ""
 color = "#ABB7B7"
 link1 = "https://tickets.degrowth.net"

content/tools/files.md

 +++
 title = "Files"
 date = 2018-09-01T08:56:20+02:00
-image = ""
+icon = "file-sharing"
 alt = ""
 color = "#ABB7B7"
 link1 = "https://cloud.degrowth.net"

content/tools/mailing-list.md

 +++
 title = "Mailing List"
 date = 2018-09-01T05:56:19+02:00
-image = ""
+icon = "bulletin"
 alt = ""
 color = "#ABB7B7"
 link1 = "https://lists.degrowth.net"

content/tools/map.md

 +++
 title = "Map"
 date = 2018-09-01T04:56:19+02:00
-image = ""
+icon = "map"
 alt = ""
 color = "#ABB7B7"
 link1 = "https://map.degrowth.net"

content/tools/pads.md

 +++
 title = "Pads"
 date = 2018-09-01T03:56:19+02:00
-image = ""
+icon = "pad"
 alt = ""
 color = "#ABB7B7"
 link1 = "https://pad.degrowth.net"