branding: Common cross app branding setting related to web fonts urls

Introduce BRANDING_FONTS_CSS_URLS setting to support loading of webfont
related css files from custom locations. By default fonts are loaded
from Google CDN servers. An essential utility setting for intranet
Synnefo deployments.

The `undocumented` setting UI_FONTS_BASE_URL is deprecated and no longer
used.
cloudbar: Apply condition on whether or not to load webfont css files
branding: Update branding-settings.conf

include default values and description for BRANDING_FONTS_CSS_URLS
setting.
ui: Remove deprecated setting from ui .conf file
webproject: Use branding webfonts css setting in 403/404/500 templates
cloudbar: Remove debug statements
cloudbar: Include url invalidation parameter based on synnefo version

make cloudbar.{js,css} unique per version to enforce client reload
between previously cached versions after synnefo upgrades.
cyclades: Check that volume type ID is an int

Make `flavor-create` command to check that the given volume type ID is
an integer.