Review quarter calculation functions

[Jennit07]

Linked to #897

The following functions need reviewed when the care home methodology is reviewed. These functions are only used in process_sc_all_care_homes which may not be needed due to variables extracted from the platform such as period_end_date which achieve the same logic and less code.

• start_fy_quarter
• end_fy_quarter
• start_next_fy_quarter
• end_next_fy_quarter

[SwiftySalmon]

process_sc_all_carehomes has been dealt with and script rewritten. Notes are on sharepoint