sysPass 2.1

Because of the major security improvements on the encryption schema, I decided to bump to the 2.1 version.

This version is focused on security as a suggestion from some contributors and my concerns on bring out a more secure app. The changes made are well (I think so) documented on the documentation site (https://doc.syspass.org), but there are a few key points worth to mention:

• Encryption schema using Defuse\php-encryption library which relies on OpenSSL
• Connection throttling for wrong log in attempts
• More secure public links by taking account data snapshot
• Improved upgrade process using tasks progress status notifications

This release needs to re-encrypt all the encrypted data, so a backup is a MUST

Please, read the docs before upgrading