Allow factional (decimal) values for Accounts_LoginExpiration

Description:

I originally reported this as a security vulnerability since we aren't able to set RC's login token expiration to less than 24 hours, and for us, that violates our security protocols.

I had not reported this as a bug because I didn't think it was a bug because the property is simply a pass-through to Meteor. However, It appears that Meteor supports fractional values for this property, thereby allowing for configuring the login token expiration to be less than one day.

We'd like to be able to set this property to, e.g. .5 -- but the RC UI does not accept decimal places for this property.

Steps to reproduce:

1. Admin > Accounts
2. locate the "Login Expiration in Days" field
3. attempt to set the field to a fractional / decimal value e.g. .5

Expected behavior:

The value .5 (and other fractional values) would be accepted.

Actual behavior:

The value is rejected and the decimal point is removed or does not appear to begin with.

Server Setup Information:

• Version of Rocket.Chat Server: 3.1.1
• Operating System: RHEL 7
• Deployment Method: Docker
• Number of Running Instances: 1
• DB Replicaset Oplog: enabled
• NodeJS Version: 12.16.1
• MongoDB Version: 4.0.9

Client Setup Information

• Desktop App or Browser Version: Chrome 81.0.4044.129 64bit
• Operating System: Manjaro Linux

Additional context

Appreciate the support here, it's important for us to be able to uphold our security protocols, and we love RC!

Start at Admin > Accounts and trace the "Login Expiration in Days" field's input validation and persistence. Verify how decimal values are handled, then test that values such as .5 can be entered and saved without losing the decimal point.