ZF Grants 2.0

[dternyak]

This PR encompasses a series of works done by the Grant.io team as a major feature release and upgrade to original version of ZF Grants.

For a more granular breakdown of the work, you can follow the history of development at https://github.com/grant-project/zcash-grant-system.

This PR includes the following features and enhancements:

• Community Created Requests
• Community signalling of support
• Proposal Subscription
• Landing Page Hooks
• Replacement crowdfunding with direct funding
• Tipping (proposal + profile)
• Price in USD
• Proposal Creation Explainer
• Pre-generated structure for new proposals
• Explainer for proposal listview
• Workflow Improvements

Closes https://github.com/ZcashFoundation/zcash-grant-system/issues/467 Closes https://github.com/ZcashFoundation/zcash-grant-system/issues/437 Closes https://github.com/ZcashFoundation/zcash-grant-system/issues/434 Closes https://github.com/ZcashFoundation/zcash-grant-system/issues/183