o [domi] Update compute so that a built-in value can also be computed. This
is required to fix a bug is sshd_config where match element values
are needlessly written to files
o [domi] Filter element according to element in SimpleUI and TERMUI
* Rework backends:
- obsolete custom backend
- move cds backend in C::M::Backend::Any child class
- move perl backend in C::M::Backend::Any child class
- Use the same backend object to read and write files
This need to move most parameters of read/write to object attributes
- Migrate file handling to Path::Tiny