v1.5.0

Many consistency fixes (managing empty values in templating, subtask plugin better error management, better retry_pattern backoff curves, variable values can be templated, ...).
Important new feature: tags on tasks. They allow for advanced task filtering via key/value pairs.

Changelog

5c34bfa Changelog for 1.5.0 (#114)
2572447 Engine: refactor task retry backoff logic (#123)
ebe4c82 Fix: engine/values: Better handling of nil and/or empty values (#112)
e7158e1 Resolution: autorun at creation (#120)
a5e4fec engine/step: Steps circular dependency check may fail on 2nd level dependencies (non deterministic order): fix (#108)
10ab459 feat: add tags to a task and an associated builtin plugin (#104)
17aff23 feat: sentry: Injects Sentry DSN URL to dashboard in order to send exception reports
6792a81 feat: uTask API server is YAML capable (#118)
30f2427 feat: variables value can be templated (#111)
dd522b7 fix(dashboard/ui): refresh home page / ergo: buttons (#119)
016af07 fix: sql: Switching JSONB indexes to GIN and enforce constraints (#109)
6070417 fix: subtask plugin exec error's return (#122)
f548024 fix: swagger-ui: use dashboard_api_path_prefix for openapi specification generation
419a839 fix: unmarshaling of database config can lead to wrong default values (#110)
e801b12 github: Removing check-boxes from pull-request templates (#117)
117f981 goreleaser: not releasing with mod=vendor anymore
07ede5d misc: building utask using Golang 1.14 (#121)
b53bd7e remove: step.Payload removed, since it was deprecated for a long time (#115)
7a59cc5 remove: vendor/ folder is deprecated, in favor of go.mod (#116)