implement tool framework and plugins

[realvitya]

Find a way to enable/disable tools on the running session
Find a way to easily implement new tool features like:

1. convert ip netmask to ip/netmasklength format (won't. use ipcalc tool plugin)
2. inspect increasing pace of counters
3. recognize user command and parse output and show it in different format (like CSV or asciitable) user command could come with a cmdline argument
4. print Organization for MAC address list for sh ip arp output (netaddr module) (done)
5. display remark for configuration which may kept in db or file for the given device

etc.

[realvitya]

A simple aspath plugin resolver is already working. Plugin system is under development and can change anytime.

[realvitya]

macvendor plugin is added to repository clicol_plugin_extra

[realvitya]

ipcalc tool is added to extra plugins