TasClient.cs: fix crash, added NULL check. Send error message (system.diagnostic.Trace.TraceError) when trying to Join Channel when there's no server connection (such as when pressing ChatTab when not yet login)

SendBox.cs: CTRL+R/G/B shortcut can auto color previous word without needing user to do selection first (increase ease of use)

TextColoringPanel.cs & others: form will auto copy current written message into coloring panel & add "copy to chatbox" button (increase ease of use significantly).