File permission special case for NTFS-3g on POSIX.

Fix issue #347, "*SensitiveFilePermissions fails on ntfs-3g mounted filesystems".
Merge pull request #378 from fiatflux/ntfs-3g

File permission special case for NTFS-3g on POSIX.
The createDefaultKnownNodes function now uses a with statement
Merge pull request #388 from Lucretiel/patch-1

The createDefaultKnownNodes function now uses a with statement
Merge branch 'master' of https://github.com/Bitmessage/PyBitmessage
Fix problem with pull request #388
Merge branch 'master' of https://github.com/Bitmessage/PyBitmessage
Adjusted size of main window back to the way it was