Moved LoginPage class and URL module to the gem

Bug: 56088
Change-Id: I2dc4e2fd005e1cee6503a6039c280e508d39f43f
Renamed remaining instances of mediawiki-selenium to mediawiki_selenium

Bug: 60820
Change-Id: I00f90b8d0346efbc923a259dc483df2fb7c89832
Moved Given(/^I am logged in$/) step to the gem

Bug: 56088
Change-Id: I5b67cb1ac0004edfec3a34ea854e205867fcffc1
Merge "Moved LoginPage class and URL module to the gem"
Merge changes I5b67cb1a,I00f90b8d

* changes:
  Moved Given(/^I am logged in$/) step to the gem
  Renamed remaining instances of mediawiki-selenium to mediawiki_selenium