Token transactions indexer

[pbca26]

As per our discussions with @piggydoughnut I'm creating this issue for transparency.

The main goal of the proposal is to replicate token transactions history API from Insight Explorer version for Tokel (e.g. https://explorer.tokel.io/tokens/3f7b2e5b66bf1bd94958f5f86aee9e4f9c4d2bc23b9230c6300ec2d04711d89b/transactions)

Since it's quite a serious amount of work I propose to break it down into following features/PRs so that all work can be done in increments for easier peer review.

• Add token create/transfer tx decoder and indexer
• Add API routes implementation to get address token transactions history
• Extend token tx decoder and indexer to collect and process DEX transactions
• Extend API routes implementation to get specific types of transactions (filter)

Feel free to drop your suggestions/comments here.