added: getSubuserDockerRepoNameTagsText

this is similar to: 
*getAvailableProgramsText(addNewLine=False, indentSpaces=0):
*getInstalledProgramsText(addNewLine=False, indentSpaces=0):

but does it for docker images themself 

e.g.
```
workerm@notebook:~$ subuser save-compressed-images docker
    subuser-firefox:Tag w ith 34
    subuser-firefox:latest
    subuser-libx11:latest
    subuser-vim:latest

workerm@notebook:~$ 
```

the funny one is where I tested spaced in tags