Explain Instruction v0.2.1-alpha

What's Changed

• Replaced popup window with sidebar integration.
• Moved description generation to background thread
• Added several missing LLIL instructions

Full Changelog: 0.1.0-alpha...0.2.1-alpha

Explain Instruction v0.1.0-alpha

Updated for Python3 and updated plugin.json so that this can be included in the official plugin manager