Function adjustDate

adjustDate(date: Date, adjustmentExpression: string): Date
Move a date forward or backward in time based on the simple adjustment expression. Example:
```
// move date forward one month
let d = Date.parse("2001-01-01")
let adj = adjustDate(d, "+1 month")
// adj now Feb. 1, 2001
```
Parameters
- date: Date
  Valid date object
- adjustmentExpression: string
  An series of date adjustment values in the format (+|-)(integer) (unit), such as "+1 year", "-1 month -12 hours". Supported units: year, month, day, hour, minute, second. Units may be in singular or plural form.
Returns Date