mainwindow: [pylint] prefix all unused arguments and variables.
mainwindow: remove "removeLayerCb".

It relied on inexistent functions in ControlContainer.
This functionnality should be evident on the layer control.
mainwindow: [pylint] DOn't redefine builtins.
mainwindow: [pylint] Remove generic try/except.

Replaced with an else if because IndexError would be too generic
to catch ^^
application: [pylint] Relocate string statement to module doc.
check: [pylint] remove generic try/excepts.
check: [pylint] remove unused variable