detectAgeInterval: Detect the age interval for some demographic data
In DDM: Death Registration Coverage Estimation

Since death distribution methods are primarily used in adult ages, it's OK to chop off the irregular infant and child age intervals (0,1], (1,5]. Further, if high ages are in different intervals this might also be a non-issue. In principal, the user should set MinAge and MaxAge to the same values used in the death distribution methods. Here we have some defaults that should almost always return the result 5 for standard abridged data, or 1 for single age data. Really there are not any other common age-specifications, but it is best to identify these and be explicit about them. We return a warning and NA if more than one age interval is used. It is assumed that ages refer to the lower bounds of age intervals, as is the standard in demography.

1	detectAgeInterval(Dat, MinAge = 5, MaxAge = 70, ageColumn = "Age")

`Dat`	a `data.frame` containing a column called `Age`, or codeage.
`MinAge`	integer ignore ages below this age.
`MaxAge`	integer ignore ages above this age.
`ageColumn`	character string giving the name of the Age column `"Age"` assumed.