Remove 'glances_' prefix from filenames.

One-line docstring should not occupy 3 lines
Expected 1 blank line *before* class docstring
First line should end with '.'
Blank line missing between one-line summary and description
No blank lines allowed *after* method docstring
Use r""" if any backslashes in a docstring

Add args visibility to the plugins to handle with the SNMP server properties (address, community...)