behat properties file to store css elements

[Rebecca Blundell]

Work on adding a properties file to make tests more readable.

[Mahara Bot (dev-mahara)]

Patch for "master" branch: https://reviews.mahara.org/7893

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/7893
Committed: https://git.mahara.org/mahara/mahara/commit/bc926b9e4269f2028515e712252aef10b1dec270
Submitter: Robert Lyon (<email address hidden>)
Branch: master

commit bc926b9e4269f2028515e712252aef10b1dec270
Author: Rebecca Blundell <email address hidden>
Date: Fri Jul 21 17:02:25 2017 +1200

Bug 1705622 - adding a properties file for some css elements

Work so far:
added switch to deal with different possible steps that have css elements
added some more css examples
changed array of css locators to const
changed const array back to array and use json en/decode as workaround
to avoid globals
made properties get_property function take an optional page location
added an optional properties param to BehatNavigation i_expand_node_in_the
added all used css elements
replaced css elements with descriptions in tests
replaced xpath elements with descriptions in tests

To do:
make the whole thing more user-friendly
look at replacing scroll to steps too

Change-Id: I83d8a96fc14701821b2e1cb37feb0900e1674f66