Added the ability to call the api for a list of endpoints

[laf]

This will now return a json response like:

{
"get_device": "http://127.0.0.1:8080/api/v0/devices/:hostname",
"get_vlans": "http://127.0.0.1:8080/api/v0/devices/:hostname/vlans",
"get_graph_generic_by_hostname": "http://127.0.0.1:8080/api/v0/devices/:hostname/:type",
"get_port_stats_by_port_hostname": "http://127.0.0.1:8080/api/v0/devices/:hostname/ports/:ifname",
"get_graph_by_port_hostname": "http://127.0.0.1:8080/api/v0/devices/:hostname/ports/:ifname/:type",
"list_devices": "http://127.0.0.1:8080/api/v0/devices",
"add_device": "http://127.0.0.1:8080/api/v0/devices",
"del_device": "http://127.0.0.1:8080/api/v0/devices/:hostname"
}

[laf]

This needs PR #312 and #314 before merging this (nothing will break if this doesn't happen - the endpoint call just won't work).