SDK v1 Release

[tayloramurphy]

Milestone https://github.com/meltano/sdk/milestone/2

### Issues
- [ ] https://github.com/meltano/sdk/issues/18
- [ ] https://github.com/meltano/sdk/pull/966
- [ ] https://github.com/meltano/sdk/issues/304
- [ ] https://github.com/meltano/sdk/issues/922
- [ ] https://github.com/meltano/sdk/issues/1354
- [ ] https://github.com/meltano/sdk/issues/1409
- [ ] https://github.com/meltano/sdk/issues/1659
- [ ] https://github.com/meltano/sdk/issues/1665
- [ ] https://github.com/meltano/sdk/issues/1667
- [ ] https://github.com/meltano/sdk/issues/976
- [ ] https://github.com/meltano/sdk/issues/1626

[tayloramurphy]

CEO notes on the Target SDK:

• Target cookiecutter and documentation could be improved
• Validating schema wasn't clear