Make wrappers for adam()

[config-i1]

This should improve the functions in terms of speed, robustness and stability.

1. es() as a wrapper of adam() with distribution="dnorm";
2. msarima() as a wrapper of adam() with model="NNN";
3. sma() as a wrapper of ADAM ARIMA;

The functions that cannot be wrappers: 4. ces() 5. gum() 6. ssarima()

This issues is related to #144

[config-i1]

Done for es() in 0d119ec433cf6134fcc9565de76703591f20bc62

[config-i1]

sma() could not be done as a wrapper, but now uses the adam() C++ code. Something similar should be done with ces, gum and ssarima.

[config-i1]

Another group of functions to amend:

1. sim.es(),
2. sim.ssarima(),
3. sim.sma(),
4. sim.gum(),
5. sim.ces(),
6. sim.oes()

[config-i1]

Given the difficulty of rewriting ces(), gum() and ssarima(), this is currently put on hold. Similar stuff applies for simulation functions.

If someone is interested in doing that under my supervision, let me know.