Changes links from osor to github in manuals
Two images of the manual are converted to jpg

There is an error with these two images using rst2pdf, so i converted
it to jpg as a workaround
Adds helper test classes
Adds a test for the correct behaviour of ToggleEditing
Previous value is not nulloed when there is an error writing it
Save button is enabled when there are changes in the view, no matter
is in edition mode or not
getChangedValues returns indexes of not changed values due to use a different
ValueWriter

In getChangedValues instead of using ValueFormatNT, the internal value writer
was being used, so when comparing numeric values it was returning values
that not really change.
Fixes NullPointerException when using navtable when alphanumeric tables.

setIconForFiltering was trying to get the selection from 'layer', but
this is a shared method with AlphanumericNavtable so 'layer' is null. The
helper method getRecordset() have to be used.
Uses EditionListener instead of LayerListener for AlphanumericNavtable
Implements the PositionListener for AlphanumericNavtable