Rework EAS account creation & ssl operation

* Fixes 2048663, 2025029, and 2100131
* Add "Trust Certificates" checkbox in EAS account creation
* Use custom ClientConnectionManager for HttpClient with registry
  for plain, ssl, and tssl (trusted ssl) connection
* Use a ConnectionPool for HttpClient connections
* Remove "Domain" checkbox in  EAS account creation
* Remove tests related to the "Domain" field
* TODO Write a test for valid usernames (requires a bit of research)
  <name>, <email address>, <domain>/<name, and <domain>\<name> are all
  valid, but there might be others

Change-Id: I4a0338df5960bfd3d679a88aaf22d1c49f49992b
5 files changed