apache-karaf 2.3.6 (new formula)

We should probably link something in `bin`, otherwise this formula isn't all that useful. But I'm concerned about the generically-named executables:

```
$ ls $(brew --prefix ./apache-karaf.rb)/libexec/bin
admin  client karaf  setenv shell  start  status stop
```

We definitely don't want this to install executables named `start`, `stop`, `status`, etc. into the user's PATH.

We can do something like

```
bin.install_symlink "#{libexec}/bin/admin" => "karaf-admin"
```

but I don't know how this software is used, so that may or may not be useful.