Version 0.30.0 with configurable font size, tooltips and usability improvements

The following are the changes for this release:

• The font size can be configured in the preferences. After that a restart of the application is required and the size of the window must be changed manually.
• There are tooltips to explain the meaning of the headings in the table.
• There is a right-click menu in the QSO History Window to edit the QSO. The text is formatted as Markdown and HTML and will be opened in the default editor for files with .md extension. They can be edited in any text editor however I recommend Visual Studio Code which can show how the text will be rendered.
• It is no longer essential to use the JS8Call log function to save a QSO History however it is still recommended. In any case if you start sending to someone else or send a CQ or Heartbeat the QSO in progress will be saved and closed.
• The QSO History button will be enabled as soon as history has been saved (previously you had to select the row again).
• The QSO History button will force the QSO History Window to show if it is already open and change it to a new call sign if necessary.
• In the main window if there is QSO History for a call sign it will be made bold in the table.
• History will be saved for a group (except for '@ HB' or '@allcall'). This is started when you send to the group and ended if you send to somewhere else.
• The history for a group will not appear in the table because the traffic will most likely be from different call signs. It can be opened from the main menu and since group names start with '@' character they will be at the top of the list.
• If you query a station that is on auto reply (say after getting a HB response) that will be saved as QSO history for that call sign.
• The findqsos function is executed in a separate process which doesn't block the U/I (that was annoying on a slower machine like a Raspberry Pi). There is a cycling "progress bar" to indicated this is happening.