New Browser Breaks Plugins that depend on non UTC date time data

[TheWitness]

Describe the bug

Some plugins written over time rely on datetime represented data. In these cases, Cacti should provide a method to represent and evaluate that data correctly.

To Reproduce

The following steps should articulate properly.

1. Some old plugin developer saves a datetime value in the settings table using the system time zone

2. Later, you evaluate that data in php using you native timezone

3. If used in the GUI, people could be confused

4. If used for logic, bad things can happen

Expected behavior

Though it's bad carma to use datetime, it would be nice if cacti provided some simple functions to flip timezones back and forth.