pages: move pagination core from blog to LiberviaPage so it can be reused: 2 new methods are available in LiberviaPage: - getPubsubExtra to generate extra data for bridge when a pubsub get is involved - setPagination to add pagination informations to template_data

import os.path

version_file = os.path.join(os.path.dirname(__file__), "VERSION")
try:
    with open(version_file) as f:
        __version__ = f.read().strip()
except NotImplementedError:
    # pyjamas workaround
    __version__ = "0.7.0D"