Release v0.5.1

[saubyk]

Updated release with the Hotfix:
https://github.com/Ride-The-Lightning/c-lightning-REST/releases/tag/v0.5.1

New APIs:

• Offers (offer, fetchinvoice, listoffers and disableoffer apis)
• Decode (helps decode offers and Bolt12 invoice strings)
• Waitinvoice API
• Listforwardsfilter (pagination support for listforwards)

Updated APIs:

• Status filtering for listforwards API
• Close channel API updated with the control for force closing

Other changes:

• Additional configuration parameter to specify the path for lightning-rpc location
• Improved logging control to reduce the log spam while running as a plugin