service enhancements

```
rearrange the service selection dialog -- it is becoming too cluttered

add tags to services for more flexible categorization, allow searching on tags;
for example IPv4, routing, addressing, security, client, server, etc.

for service customization, instead of using various tabs, allow
files/dirs/commands to be added to a stack/tree

add service dependency packages and/or binary checks to inform users when
required deb/rpm/etc is not installed

extend services to specify certain options that change the behavior of
auto-generated config output
examples:
- OSPF fast convergence
- SSH root login
- DHCP address pool
- apache web root

copy service selections between nodes (e.g. "apply to multiple" button)

```

Original issue reported on code.google.com by `ahrenh...@gmail.com` on 23 Aug 2013 at 5:51