Give sharers, boarders and lodgers their own rent, tenure and LHA category

[MaxGhenis]

Families other than the household head's have no rent in the model, so they get no Universal Credit housing costs element or Housing Benefit:

• rent is a household input (FRS HHRENT), and personal_rent gives all of it to the household head. Every other benefit unit has benunit_rent = 0.
• UC housing support and HB read the household's tenure, so a lodger in an owner-occupied home counts as an owner.
• The LHA category counts every adult in the household as a non-dependant and uses the never-populated is_shared_accommodation.
• Non-dependant deductions are charged to every benefit unit for everyone outside it.

This leaves out:

• joint tenants and other sharers in FRS shared households (HHSTAT 2), who are liable for part of the rent;
• boarders and lodgers, who pay the householder.

What the law requires:

• UC Regs 2013 Sch 1 para 2(b) and Sch 4 paras 9, 10, 20 and 24-29.
• HB Regs 2006 regs 3, 12B(4), 13(7), 13C, 13D and 74(5), and Sch 1 para 2.
• CTR: SI 2012/2885 reg 9(2)(d)-(e) and Sch 1 paras 7(3)-(4) and 8(5), with the Welsh and Scottish equivalents.

The householder side (rent received, rent-a-room relief, disregards) is #2002.