Set <Control>V as the accelerator for the 'View in Finding Chart' button

Add a new method, LEMONJuicerGUI.handle_view_in_chart_accelerator(),
and connect to it the <Control>V accelerator. This method determines
what is the star (StarDetailsGUI) being shown in the current page in
the gtk.Notebook and clicks its 'View in Finding Chart' button.
Hide the Finding Chart when we click on the window's close button
Fix the 'Save' button on the matplotlib navigation toolbars

Although the matplotlib navigation toolbars under the light curves and
the finding chart work, allowing the user to navigate through the data
set, clicking on the 'Save' button raises the "TypeError: parent must
be a GtkWindow or None" exception. The reason for this is that we are
passing a gtk.HBox object as the second argument to the __init__()
method of the NavigationToolbar class. Use gtk.Widget.get_window() to
get the widget's gtk.gdk.Window that NavigationToolbar expects.
Suggest relevant filenames in the 'Save' button gtk.FileChooserDialog

The filename that is suggested by the gtk.FileChooserDialog when the
user clicks on the 'Save' button on the matplotlib navigation toolbar
is the string returned by FigureCanvas.get_window_title() or, in case
there is no window containing the figure, a generic 'image'.

Monkey-patch FigureCanvas.get_window_title() so that, instead of the
vague 'image', the file chooser suggests a relevant filename: (a) the
name of the observed field (as returned by LEMONdB.field_name), if we
are saving the finding chart, and (b) a string containing the name of
the field, the ID of the star and the photometric filter, in the case
of light curve plots.
Fix grammar error — it's "to which to assign"
Add missing whitespace after assignment operator
Add missing whitespace between words
Add the --individual option

Make it possible to do photometry using aperture and sky annuli
derived from the FWHM of each image, instead of using the median FWHM
of all the images in the same filter. As concisely explained by Javier
Blasco in issue #4, a fixed aperture may enclose different percentages
of the stars, and therefore lead to suboptimal signal-to-noise ratios,
when the seeing is variable and the aperture small.
Fix outdated references to the --pp, --ip and --kp options
Abort the execution if conflicting options are specified

The --annuli option (read the photometric parameters from the XML
file) is incompatible with --individual (derive the parameters from
the FWHM of each image on which photometry is done). Both conflict,
also, with --aperture-pix, --annulus-pix and --dannulus-pix, which
set these parameters to a fixed value.