Adds nickname command for friendly command prompts

[mmattozzi]

Adds the nickname command, command line argument, and properties file property to reflect a friendly name in the command prompt and !list command.

0: jdbc:oracle:thin:@localhost:1521:mydb> !nickname devdb
0: devdb> !list
 #0  open     devdb              jdbc:oracle:thin:@localhost:1521:mydb
0: devdb>

OR invoke at command line:

$ sqlline -u jdbc:oracle:thin:@localhost:1521:mydb -n user -p pass -nn devdb

OR use in a properties file:

url=jdbc:oracle:thin:@localhost:1521:mydb
user=user
password=pass
nickname=devdb

I originally wanted to name this command alias and use a -a option at the command prompt, but I realized that alias and unalias also seemed to be reserved for a future command alias function, so I went with nickname. I was also a little confused about which documentation files were autogenerated and which I needed to update. Let me know if I missed any!

[julianhyde]

Fixed in ba9dd38.

Thanks for the PR, @mmattozzi! Nice work.