Ant build and package.properties improvements

[prrvchr]

This PR is supposed to fix issue #127

• Class-Path has been added to the MANIFEST.MF file.
• No other archive is created when generating the build.xml file.

In addition to these two fixes, the management of the package.properties file has been revised to correct the following problems:

• When deserializing (ie: reading the package.properties file), if any resources are missing or modified, a message will be logged and the file marked as modified (ie: isDirty() returns true).
• When saving if there are any pending changes (ie: if you used the text editor or when opening missing files are displayed) then the text editor will be reloaded.
• A specific listener for refreshing the widget (ie: ContainerCheckedTreeViewer) has been implemented.
• All listeners loaded on initialization are now removed during dispose().
• Hidden files and/or folders (ie: starting with dot) management is now supported.
• It is now possible to include a folder in the selection if it is empty (ie: no visible members).

I must be forgetting things but I remain available for any information and thank in advance for the reviewer.