Apply PEP 8 style guidance to zenmap

Using the pep8 tool (https://pypi.python.org/pypi/pep8), fixed the
following style issues:

Count   Issue
11      E201 whitespace after '['
8       E203 whitespace before ','
41      E211 whitespace before '('
11      E221 multiple spaces before operator
61      E225 missing whitespace around operator
237     E231 missing whitespace after ':'
91      E251 no spaces around keyword / parameter equals
19      E261 at least two spaces before inline comment
41      E301 expected 1 blank line, found 0
200     E302 expected 2 blank lines, found 1
356     E303 too many blank lines (2)
563     E501 line too long (106 characters)
39      E701 multiple statements on one line (colon)
13      E702 multiple statements on one line (semicolon)
4       W291 trailing whitespace
2       W293 blank line contains whitespace
8       W391 blank line at end of file
21      W601 .has_key() is deprecated, use 'in'
2       W602 deprecated form of raising exception

The remaining issues are long lines due to very deep data structures. I
chose not to alter them, as it would involve backslash-continuation
where whitespace is not permitted:

./zenmapGUI/ScanInterface.py:323:80: E501 line too long (90 characters)
./zenmapGUI/ScanInterface.py:456:80: E501 line too long (84 characters)
./zenmapGUI/ScanInterface.py:464:80: E501 line too long (84 characters)
./zenmapGUI/ScanInterface.py:472:80: E501 line too long (122 characters)
./zenmapGUI/ScanInterface.py:479:80: E501 line too long (122 characters)
./zenmapGUI/ScanInterface.py:920:80: E501 line too long (94 characters)
./zenmapGUI/ScanInterface.py:923:80: E501 line too long (93 characters)
./zenmapGUI/MainWindow.py:575:80: E501 line too long (99 characters)
./zenmapGUI/MainWindow.py:906:80: E501 line too long (99 characters)