Make the toolbox a package

[ilent2]

It would be good to make the toolbox into a package, this will reduce namespace pollution. The functions can be used individually, such as

ott.force_z(...)

or all the functions can be imported

import ott.*

This will require adding the above import to all toolbox functions that use other toolbox functions and changing the directory ott-toolbox to +ott, however this change breaks backwards comparability.

[ilent2]

Done in 4b36dff