Logging Enhancements (Revision #4)

- Help/View Log menu option invokes Log Viewer dialog which works independently of the normal log file.

Log Viewer dialog:

- starts with an empty log table

- accumulates entries logged after the dialog has been opened

- Save to File, Save to Clipboard (This will work on current row or selected rows.  A copy always copies rows.)

- allows to set filter by level

- intercepts stdout, stderr and uncaught exceptions in the "Console" tab

By default, a rolling file logger is always enabled to ~/.datastudio/datastudio.log

This logger is configured to write up to 3 files of up to 300KB each, using "%d{M/d HH:mm:ss.SSS} %C{1}.%M %m%n layout.  (Logging month/day per Tanya's request).

This logger can be turned off by placing logger.config file into ~/.datastudio directory.  This file overrides built-in configuration and offers the developers or end users virtually unlimited configuration choices.