v2.1: QoL improvements

Note: v2.1 has a last minute bug, please switch to v2.1.1 or newer

Mostly technical update with Quality of Life improvements, including (since v2.0):

• Fix possible bug with unquoted user text;
• Ignore some most-likely-to-happen errors with callback alert if they happen;
• Show "server time" hint on admin messages;
• Use HTML parse mode as default.