improvement: getUserCommandLine

added to previous pullrequest an enhancement: getUserCommandLine(argvList, commandOptionList, allowOnlyOptions=False):
e.g. in `subuser list` does only allow option to be set but not any specific program names

e.g. code: from the `list` command I adjust
```
commandOptionList = ['--available', '--installed', '--short']
userProgramList, userOptionList = subuserlib.utils.getUserCommandLine(sys.argv[1:], commandOptionList, allowOnlyOptions=True)

```
user calls it like `subuser list firefox --installed`
```
workerm@notebook:~$ subuser list firefox --installed
INPUT-ERROR. command input was: <firefox --installed> 

Only Command Options are allowed: <--available --installed --short> 

For mor info see the help: `subuser -h`
workerm@notebook:~$ 


```