[Behat] Added possibility to read browser logs multiple times

[mnocon]

Question	Answer
Tickets	https://jira.ez.no/browse/EZP-31453
Bug fix?	no
New feature?	yes (for tests)
BC breaks?	no
Tests pass?	yes
Doc needed?	no
License	GPL-2.0

Notes

• CS fixer failure is unrelated and will be fixed in another issue: https://jira.ez.no/browse/EZP-31578
• this PR contains a TMP commit that will be removed

Description

According to Selenium doc (https://github.com/SeleniumHQ/selenium/wiki/Logging#retrieval-of-logs):

In the scenario where a log is retrieved several times the same log entries should not be retrieved more than once. 
For this reason, and to same memory, after each retrieval of a log the log buffer of that log is reset.

It's not possible to retrieve the same log multiple times. As this is the approach used in ezsystems/allure-behat#10 I had to introduce a "cache" layer that allows to read the same log entries twice (but no more 😉 ).

There is also one small change: Webdriver can return null when the session is not started yet, this case is now handled.

To do before merging:

• Rebase with 1.5 to resolve CS issue
• Remove TMP commit