avocado.core.output: Rename OutputManager() to View()

As this class is evolving to become the one stop shop
for avocado output needs. Also, move some methods around
to help organize better the class layout.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
avocado.plugins.runner: Port to View() class

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
avocado.core.output: View() API overhaul

Organize the log APIs into:

* APIs that log operation statuses (.log_ui_status)
* More generic ones (.log_ui)

The distinction helps and gives more insight on what is
actually accomplished by each method. This is a fairly
intrusive change, although it received a fair bit of
testing before submission.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>