[backend] Logging should be done through libunity-2d logging facilities

[Aurélien Gâteau]

libunity-2d provide some logging facilities which features a few advantages over standard q(Debug|Warning):

- Print the class and method name of their caller.

- Get colored output (conditional in a branch I have not yet published)

- Handy way to debug a variable: UQ_VAR(foo) will output the following:
  foo=<value-of-foo>

- Handy glib-like RETURN_IF_FAIL and RETURN_VALUE_IF_FAIL macros

- Handy (not yet published) way to print the time since startup (togglable with an environment variable)

This should be cleaned up and we should start using it instead of q(Debug|Warning)

[Richard Dale (rdale)]

The attached patch changes all instances of qDebug() to UQ_DEBUG, and all instances of qWarning() to UQ_WARNING

[Aurélien Gâteau (agateau)]

Thanks Richard, just applied your patch.