aam.fitter, clm.fitter, sdm.trainer packages

Follows #431.

1. Moves `AAM` and subclasses from `aam.builder` to `aam.base`
2. Moves `AAMFitter` and subclasses from `aam.base` to `aam.fitter`
3. Moves `CLM` and subclasses from `clm.builder` to `clm.base`
4. Moves `CLMFitter` and subclasses from `clm.base` to `clm.fitter`
5. Moves `SDTrainer` and subclasses from `sdm.base` to `sdm.trainer`
6. Moves `SDFitter` and subclasses from `sdm.base` to `sdm.fitter`