[set-user-quota] Adjustments

[eviltwinhans]

Overview

set-user-quota is to be adjusted.

Description

• set-user-quota without options should lead to an error message (with info about valid values) instead of making quota unlimited
• set-user-quota -j infinity/<float>/<negative int>/<any other non-valid values> should lead to an error message with information about valid values
• set-user-quota -j <zero or positive int> should set user's limit of parallel jobs to the required value
• set-user-quota -j unlimited should make user's job quota unlimited
• set-user-quota --help should contain information about valid values

Follow up actions

• If needed, FE should be adjusted to correctly map unlimited parallel jobs (e.g. 'unlimited' instead of 'infinity')
• Documentation should be updated