Arguments checking 2.0

Freezer provides a lot of arguments for user.

Some of arguments are easy to check: action can be "restore" or "backup".

Some arguments have only meaning when they are using in batch: lvm-snapsize is useless without --lvm-dirmount.

Some arguments can look good, but be wrong by the state of environment:

we can have no abs_path
or lvm-snapsize can be bigger then enough to make a snapshot

It would be great to have a system for complex parameter validation. Current one works fine for single arguments, but doesn't support complex checking.

It is better to have all our checks in one place, without affecting other code.