Text updates for SUL rename request

Apply text changes requested by the product owner for the SUL rename
request form:
* Direct the user to SUL documentation
* "projects" -> "Wikimedia projects"
* "your username" -> "this username"
* "other wikis" -> "other Wikimedia wikis"
* "go forward" -> ""
* "Select a new username" -> "Request a new username"
* "to project stewards" -> "to Wikimedia stewards"
* "you will be notified" -> "you will be notified by email"
* "This is your current username. It will be changed to the name you
  choose." -> "This is your username now."
* Add colons after Requested username, Email, and Confirm email
* "via" -> "by"

Change-Id: I1e18973260d1b89283b892ae9371761785538f68