* Declare functions swapon() & swapoff(), is_swap() & reswap().
* Apply swapon/swapoff for states mounted, unmounted, remounted and
absent.
* Override default opts and boot when fstype=swap.
* Do not honor 'fstab' when fstype=swap (fail instead).
* Also fail when fstype=swap and 'path' is not 'none' ('-' for Solaris).
* Update module documentation accordingly.
+ Replace all platform.system() calls by a variable.
refactor integration tests
* Improve readability/understanding of what is tested, and what OS is
targeted.
* Move 'swap' related test cases into dedicated file (swap.yml).
* Add new test cases about swap enabling/disabling.
* Extend tests to FreeBSD when possible.
