Point and vectroized numerical functions

[Qazalbash]

Description

This issue is the extension of #15 and #18, where we need different functions depending on the type of input and workload distribution.

Suppose we have a function that is logpdf of a distribution. I propose to have two different functions for this:

1. logpdf_x takes a single value and returns a single value.
2. logpdf_v takes a vector and returns a vector, using vmap.

The same can be done for other functions like pdf, cdf, logcdf, logppf, ppf. This will provide a lot of flexibility to the user.