Python: decouple Python iface from native binding

With this patch, all the SWIG stuff is isolated into
nativebt.i, whereas the real Babeltrace Python interface
is plain Python in bt.py.

The Babeltrace Python binding is now a Python package, but
backward compatibility with the original module is ensured
by importing all public symbols from the bt module in the
package itself (__init__.py), which is named like the
original module, babeltrace.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: remove explicit inheritance from object

This is a Python 3 binding, and all classes are new-style
classes in Python 3, so there is no need to inherit from object
explicitly.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: bt.py: PEP 8 + improve readability

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: remove useless 'return None'

A Python function's default return value is None already.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: bt: do not expose ClockType

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: document TraceCollection

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: CTFWriter: FloatFieldingPoint -> FloatingPointField

Human error. Since CTFWriter.FloatFieldingPoint is
publicly exposed, we keep it there, making it inherit from
CTFWriter.FloatingPointField.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: CTFWriter: add FloatingPointFieldDeclaration

This class is added in order to keep the API
consistent, as there is a FloatingPointField class.
It inherits FloatFieldDeclaration so that the API is
not broken.
Python: CTFWriter: forbid Stream.__init__()

In the CTF writer API, a Stream object may only
be created using Writer.create_stream(), therefore
rendering Stream.__init__() useless for the user,
since the resulting object is not, and cannot, be
associated with a Writer object.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: document print_format_list()

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: document TraceHandle

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: document CTFStringEncoding

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: document ByteOrder

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: document CTFTypeId

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: document CTFScope

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: document Event

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: document FieldError

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: document EventDeclaration

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: document FieldDeclaration

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Python: document IntegerFieldDeclaration

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>