pasty v1.0.0 (stable)

[lus]

This PR tracks the process of refactoring and improving pasty in many ways. It also introduces Semantic Versioning to this project, so its completion will equal the v1.0.0 release.

ToDo:

• [x] refactor general package structure
• [x] refactor code structure (e.g. removing singletons)
• [x] limit storage driver support to PostgreSQL & SQLite (#39)
• [x] remove v1 API support
• [x] switch from valyala/fasthttp to net/http
• [x] embed the web frontend (#37)
• [x] implement proper logging (#32)
• [ ] implement Semantic Versioning workflow(s) (#41)
• [x] fix bug(s) (#42)
• [x] implement console commands (#16)
• [ ] implement measurements to prevent data corruption when updating to v1.0.0

Other issues not mentioned here will be dealt with after the v1.0.0 release.