chore(gitignore): ignore browser/dev-tasks/e2e/protractor.conf

The protractor.conf file is created during e2e tests and should not be
in version control, so add it to a .gitignore file.
login/logout moved to /v1/session
issue #231 new get session endpoint for logged in user
fixes issue:220, non-existent question id should be 404, not 500
e2e: cleanstart: do not run if not OSX and/or no mlvm install

Echo error and exit if either not OSX or mlvm command not present in
shell.
browser(authentication): use new endpoints

Endpoints now consistently use 'session' for URL.

Remove overrides to endpoint addresses, make corresponding changes to
tests, and fix schema/validation and response-handling bugs.
accept empty comment and answer objects for ask issue 241
browser: updates to package.json
e2e: begin multiCapabilities
e2e(java): gradlew path for windows

On windows, use 'gradlew.bat' instead of './gradlew' to launch gradle
commands.