[8.0] crm_claim_summary_report: text overlaps, signature line and letter paper

Created by: yaniaular

Improvements:

1. Add line for customer's signature in the customer copy and support copy.
2. The paper of the report should be letter
3. Text overlaps in the report:

https://github.com/Vauxoo/addons-vauxoo/blob/8.0/crm_claim_summary_report/reports/claim_summary_report.xml#L93-L112