Return strings instead of byte sequences/ints

- IP addresses
- MAC addresses
- (B)SSIDs

Are now all returned in human-readable form instead of as
bytestrings/ints
Whitespace
Add missing interfaces/constants
Do something nice with AccessPoints
Decode UTF-8 SSID's properly
Add missing files to MANIFEST.in
Make GetSecrets do what the spec says

The spec says that if the parameter to GetSecrets is empty,
NetworkManager returns all available secrets. Instead it throws an
exception. I find the intended behaviour more useful, so let's make that
happen.
Firest steps for preprocess: AddConnection

To make it easy to rounf-trip data, we'll preprocess it to do the
inverse of postprocess.
Reduce code duplication
Add preprocess to Update() and AddAndActivateConnection()
VPN ipv4 preprocessing
Documentation rework
Add debugging functionality
Use 'I' in struct.pack and not 'L'.

On x86_64, 'L' gives an 8-byte string. 'I' gives a four-byte string on
x86 and x86_64.
Version 0.9.7
Merge branch 'master' into debian
New debian package
Packaging fixes