Feature #3371: Make quotas optional for new users

(cherry picked from commit 0bdf5645b7139716409d8422c585c41299dba958)
Feature #3371: Make quotas optional in updates

(cherry picked from commit ddfbbfaa0d4ea76fb783fea850b8bd688bd0ecaf)
Bug #3123: Add unlimited and default quotas in user creation

(cherry picked from commit e426554a2ef48ed34abd2c743084532a9afbe9e8)
Bug #3123: Add unlimited and default quotas in user update

(cherry picked from commit 16a69702b6741dd4971580e5b94ee09b1db61e95)
Bug #3123: Do not round mem quotas in update

(cherry picked from commit cbc3e49c318f7e4ac746c370b45549aae773b460)
Bug #3123 #2501: Show default VM quotas even if the usage is 0