[prosEO CLI] UX: Documentation is ambiguous - command 'login'

[dlr-tangosierra]

Testing parameters:
User Login: no user login
Mission : no mission

Context:
The help documentation ('help') for the command 'login' is a bit ambiguous. It could infer that all commands are valid to be used with login apart from 'mission show'.

Example output:
login Log in to a mission in prosEO. A login is required prior to executing any other command except "mission show".

Further information:
A potential enhancement would be to write "any valid command except..."

[tangobravo62]

Help text reworded:

prosEO> login -h
Log in to a mission in prosEO. All valid commands except for "mission show" require prior login.
[...]