Rename aeidon to aeidon_import

to avoid module name confusion (between the original module and the advene plugin)
Fix variable name
gui.edit.shapewidget: implement opacity setting
gui.edit.shapewidget: add filled option for Line
core.controller, gui.main, util.importer: _fieldnames is a set()
share/exporters.xml: implement metadataplayer export view
util.helper: display --:error:-- string for invalid timestamps
gui.plugins.videoplayer: fix select_file action
gui.edit.shapewidget: define __unicode__ method for Shape classes
core.plugin: display exception message in case of ImportError