Integration tests - BaseWebObject class

I added BaseWebObject, a base class for all web element objects,
i.e. both page objects and regions.
The new class now contains several wrappers for driver's
capabilities, which are required not only by the pages but other
webelements as well, and used to be located within pageobject.
The necessity arose while discussing the regions patch
(https://review.openstack.org/#/c/102227/), that will be
modified accordingly by tnovacik.

In addition, I've made 6 methods private, as they should
not be used outside the pages, definitely not by the tests.

Partially implements blueprint: selenium-integration-testing
Closes-Bug: #1354017
Closes-Bug: #1356774

Change-Id: Id65951160b2016cbdafd8417df48b1b5cd02f99f
Merge "Integration tests - BaseWebObject class"