Yet another group of Checkstyle fixes

- Split the zoomMinMax method into three parts (creating the minAndMaxAreInvalid and setDomainRangeCharts methods).
- Created ZOOM_IN_COMMAND, ZOOM_ORIGINAL_COMMAND and ZOOM_OUT_COMMAND constants for handling these zoom commands (which solves some Checkstyle issues).
- Created DIMENSION_5X0, DIMENSION_10X0 and DIMENSION_0X10 constants for GUI layout.
- Created ZOOM_X_AXIS_DEFAULT_START and ZOOM_X_AXIS_DEFAULT_END constants for zooming along the x axis.
- Created CHART_FRAME_TITLE_PREFIX constant used for titles of the chart frames.
- Added punctuation for Javadoc comments (JavadocStyle, see http://checkstyle.sourceforge.net/config_javadoc.html).
- Put some trailing comments on a separate line (TrailingComment, see http://checkstyle.sourceforge.net/config_misc.html).