UI: Update XML UI descriptions, remove deprecated VBox/HBox/HButtonBox.
Log: Introduce logging fun without popups.

Popups are still being popped, they have yet to be discarded.
Log, Simulation: Add logging cap of GError, replace simulation popups by log lines.

Part one of many to fix this annoyance.
UI: Fix Part selection panel orientation.
Log: Change GError logging to use more arguments.

Allows additional context text to be added before the actual error is printed as a line.
This allows for easier/faster diagnosing errors such as "can't open file".
schematic.c: Get rid of whitspace issues.
SchematicView: Start using Log instead of Dialog based error messages.

Fixes also memory leaks, logic errors.
Also gets rid of all whitespace issues.
SimSettings: Use Log instead of Dialog based popups for error displaying.

Also gets rid of all whitespace errors.
Simulation: Use Log for log messages.

Also removes a bunch of whitespace errors.
schematic-view.c, textbox-item.c: Properly name GtkBuilder variables as `builder`.

`gui` is not correct, the builder just parses a XML .ui/.glade/.builder file but is not tied to the lifetime of the UI itself.
SchamticView,UI: Embed LogView into a scrolled window, make the oregano-main.ui paned vertically.
netlist-helper/editor.c,ngpsice.c: Continue replacing error dialogs by log entries where possible.
LogView: Introduce user selectable visibility for LogView.

TODO: Show on new errors, or at least blink the button red-ish.
SchematicView: Use a sane stock icon for the logview toggle button.
SchematicView: Never hide the logview, just minimize the pane.
Log,Engine: Dispatch log_append_error to log_append if error is NUL, closes #129.

Also fixes a logic flaw in the error handling code of the NgSpice process.
SchematicView: Factor initial size calc into its own function.
UI: Rearrange the logview and sheet canvas.

So the part selection pane does not change size on visibility change of the logviewer.