* Add previous, current and next forms to form handler
* Add current, previous and next sales forms to form handler
* Implement current_lettings_form, current_sales_form and store year and form type in form
* refactor lettings_forms
* Use current, previous and next forms in lettings log model
* Use current, previous and next forms in sales log model
* use current, previous and next forms in csv service
* Remove "startyear_endyear" forms from form handler
* Remove name from form initializer and add an optional start year
* refactor get_form
* update csv test, fix form initialize
* rebase fix
* Refactor form_name_from_start_year method out
* remove unused variable
* fix typo, add date tests
* rebase, fix tests
* add comment to before test block
* Change the FormHandler back to only contain the form objects
* extract name
* Change property major repairs date validation from 2 years to 10
* add voiddate_date_in_soft_range? and major_repairs_date_in_soft_range? methods
* update error messages for hard validations
* Add property_major_repairs_value_check to the form
* add void_date_value_check and fix some namings
* Update value_check hidden in check answers to depend on whether the questions is answered
* Remove a schema key
* extract constants for number of days
* change error messages wording
* update schema and csv files
* Update keys of rsnvac for first lets
Making it match with what is in the data dictionary. It was a wuick enough
fix to be included in this branch since it pairs well with the newprop derived
variable implementation
* add newprop derived variable and tests
* fixes
* use ternary statement for newprop derivation
* Remove enums
* Add some convenience methods to make validations more readable
* Gender chars instead of ints
* Remove incorrect API doc info for now
* More convenience methods
* Rename label from value method
* Wrapper hbrentshortfall
* Please the cop