Move To Error Actions

It would be convenient to be able to move the cursor the next (or previous) error.  This was accomplished be adding two additional actions, one for moving the cursor to the next error and the other to move the cursor to the previous error.  Each action was given an arrow icon, which were modified to have a red hue.  Both were also assigned key shortcuts, which were Ctrl+. (period) for next and Ctrl+, (comma) for previous.  These keys were chosen because they also contain the greater than and less than keys, which are like arrows.

The actions are automatically connected to associated triggered functions in the MainWindow class, which call new functions in the EditBox class to perform the action.  These functions first find the error for the current line.  If the current line does not have an error, the find returns the index of next error or will return in index one beyond the end of the error list.  The functions then move to the next or previous error depending whether the cursor is already sitting at the error found.  If beyond the last or first error, a question box is displayed informing this and asks whether to move to the first or last error in the program.  If there is only one error, then no question box is displayed.

There is some sort of issue when running on Linux (Mint 13 KDE) using the static QMessageBox::question() function to display the question asking whether to wrap around and to the first or last error - an X Error message is output.  This may have something to do with another problem where there is suppose to be a question mark icon on this message box, but the information icon is displayed instead.  These problems do not occur on Windows and also do not occur on Linux if the application is launched with the -style Plastique option.

For now the next and previous error tool bar buttons and edit menu items are always enabled.  Next these will be disabled when there are no errors.

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