Improve Popups feature: v2

[mendorshikh]

• Fix the success emails (transactional) after a submission. Because the success email is not sending to the users properly.

• Add and preserve the formatting of the for success email content. At the moment, it is just basic text.

• Add the "Submit Once" option. Once a submission is received, the popup will now show. We don't want to display the same popup over and over again if the customer has already filled it out.

• Date and Time validation should be separate fields aside from being a single field. For example, if users want to collect birthdays from customers, the current popup field is asking for a year/month/day and hour/minute.

[mendorshikh]

Link to feature: https://erxes.productboard.com/feature-board/planning/features/5260111