Able to change Proxy Port

[NghiaTranUIT]

Description

After the Preference -> General tab is implemented #20, we should support this Proxy Port

Acceptance Criteria

• Only number in the text field
• Port valid from 1024 to 49151
• Display the error text field if the port is invalid
• If the port is valid, change the Proxy Port of the Core. (Stop/Start the core with new port)
• The port number is persisted.
• Default port is 9090
• System bar is updated