SQLite local storage

Adding local storage capabilities, beyond or in parallel to AWS/remote storage

Fixing compatibility Python 3.6

Fixes to v0.6.1 with compatibility issues with old Python 3.6

Decoupling storage

• Refactored the storage access to make it extensible to different storage solutions. Currently it is tied in to AWS DynamoDB, but with these changes, more storage solutions (cloud based or local can be added)
• improved the load and save commands to make them in encrypted mode by default. Decrypted mode can be forced with the -d option