Extension of oozie's expression language to support more functions in input/output instance definition:

Oozie coordinator supports coord:current to specify start and end instances for input datasets. coord:current is always resolved wrt job's nominal time. If we change the job start time, we also have to change start and end instances of inputs/outputs. Else, it will pick up wrong values. So, the following functions are added to oozie's EL:
1. now(hr, min) - Adds hr and min to current nominal time
2. today(hr, min) - Adds hr and min to start day of nominal time
3. yesterday(hr, min) - Adds hr and min to start of previous day of nominal time
4. currentMonth(day, hr, min) - Adds day, hr, min to start month of nominal time
5. lastMonth(day, hr, min) - Adds day, hr and min to start of previous month of nominal time
6. currentYear(month, day, hr, min) - Adds month, day, hr, and min to start year of nominal time
7. lastYear(month, day, hr, min) - Adds month, day, hr and min to start of previous year of nominal time

For example, if the job is running at 5th hour of the day and hourly input should be all of previous day and first 2 hrs of today, input can be defined as:
start - yesterday(0, 0); end - today(2, 0)