Cisco Switch/Router Interface management

This patch introduces managing remotely cisco IOS network devices
through ssh or telnet with a puppet type/provider.

This patch allows to manage router/switch interface
with the interface type:

interface {
"FastEthernet 0/1":

		device_url => "ssh://user:pass@cisco2960.domain.com/",
		mode => trunk,
		encapsulation => dot1q,
		trunk_allowed_vlans => "1-99,200,253",
		description => "to back bone router"

}

It is possible with this patch to set interface:

• mode (access or trunk)
• native vlan (only for access mode)
• speed (auto or a given speed)
• duplex (auto, half or full)
• trunk encapsulation
• allowed trunk vlan
• ipv4 addresses
• ipv6 addresses
• etherchannel membership

The interface name (at least for the cisco provider) can be any
shorthand interface name a switch or router can use.

The device url should conform to:

• scheme: either telnet or ssh
• user: can be absent depending on switch/router line config
• pass: must be present
• port: optional
• an optional enable password can be mentioned in the url query string

Ex:
To connect to a switch with a line password and an enable password:
"telnet://:letmein@cisco29224XL.domain.com/?enable=letmeinagain"

To connect to a switch/router through ssh and a privileged user:
"ssh://brice:letmein@cisco1841L.domain.com/"

Note:
This patch only includes a Cisco IOS provider. Also terminology adopted
in the various types are mostly the ones used in Cisco devices.
This patch was tested against:

• (really old) Cisco switch 2924XL with ios 12.0(5)WC10
• Cisco router 1841 with ios 12.4(15)T8
• Cisco router 877 with ios 12.4(11)XJ4
• Cisco switch 2960G with ios 12.2(44)SE

Signed-off-by: Brice Figureau <brice-puppet@daysofwonder.com>