Make merged module descriptions more grammar.

This changes the behavior of description merging in Metasploit's console. Instead of having a trailing message of the merged description data, the data is now its own sentence. This seems to be the intent, anyway; there is no case where you'd want this to be a sentence fragment. This bug came up during #3509.

## Verification

- [ ]  `msf > info payload/windows/meterpreter/reverse_hop_http`
- [ ] See the grammaticalness.

## Merging reminder

If you merge this, remember to say `FixRM #8828` in the commit message somewhere.