Add shell:wc command for KARAF-2164

Adding support for a `shell:wc` command in Karaf :)

```
        __ __                  ____
       / //_/____ __________ _/ __/
      / ,<  / __ `/ ___/ __ `/ /_
     / /| |/ /_/ / /  / /_/ / __/
    /_/ |_|\__,_/_/   \__,_/_/

  Apache Karaf (2.3.2-SNAPSHOT)

Hit '<tab>' for a list of available commands
and '[cmd] --help' for help on a specific command.
Hit '<ctrl-d>' or type 'osgi:shutdown' or 'logout' to shutdown Karaf.

karaf@root> echo "hello world" | wc
        1       2       13
karaf@root> wc LICENSE
        475     4053    28230   LICENSE

karaf@root> wc LICENSE README RELEASE-NOTES
        475     4053    28230   LICENSE
        77      562     3933    README
        1831    16765   118449  RELEASE-NOTES
        2383    21380   150612  total
karaf@root> cat LICENSE | wc -l
        475
```

Let me know your thoughts on any improvements and such

Alan