Merges v0.2.1 changes to master (#612)

* Fix setup wiki article link in readme (#594)

* add snapshot file to releaser archives (#592)

* Double spend check (#606)

* Fix: added a check for doublespends

* Fix: added a check for double spends

* Fix: fixed iport cycle

* Feat: replaced error with error variable

* Feat: store tangle in factory

* Update dapps/faucet/packages/faucet.go

Co-authored-by: Wolfgang Welz <welzwo@gmail.com>

* makes send tx web API handler synced

Co-authored-by: Hans Moog <hm@mkjc.net>
Co-authored-by: Wolfgang Welz <welzwo@gmail.com>
Co-authored-by: Luca Moser <moser.luca@gmail.com>

* Adds tips broadcaster to gossip plugin (#608)

* adds tips broadcaster to gossip plugin

* adds missing for loop

* addresses review comments

* bumps network and database versions (#610)

* Revert "bumps network and database versions (#610)"

This reverts commit 3e626eac.

* Revert "Revert "bumps network and database versions (#610)""

This reverts commit 9aa3d1bb.

* Adds blacklist and PoW requirement to the faucet (#609)

* adds blacklist and PoW requirement to the faucet

* fixes wrong condition to check pow

* fix faucet payload marhsaling

* don't test payload data if not payload data set

* updates changelog for v0.2.1 (#611)

Co-authored-by: Rajiv Shah <rajivshah1@icloud.com>
Co-authored-by: Wolfgang Welz <welzwo@gmail.com>
Co-authored-by: Hans Moog <3293976+hmoog@users.noreply.github.com>
Co-authored-by: Hans Moog <hm@mkjc.net>