Add lvm meta pool and starting of pv/lvm_meta size calculation refactoring.
[disks] fix syntax errors
[disks] do not create new lvm_pool if disk already has it
Many fixes for lvm calulcation
* recalculate free_space for each initialization
* don't create new boot partition\type if we already have it
* add free_space field for nailgun internal usage
* reimplement set_pv_size method, now with lvm_recalculation (we just remove and create new PV)
[disks-convertor] fix lvm calculation
[disks] fix tests
[js] Revert minimum size of VG for disk
commit e872cec09007c5e0a13c003bb75f81c2f4fcc0cd
[disks] Add comments
[disks] fix pep8