Add support for multiple sessions in a browser

Fixes gh-49
users sample password type=text->type=password

Change the password input of the users sample from type of text to type
password.

gh-49
Update CookieHttpSessionStrategy default parameter from u to _s

This both provides two things:
- more meaningful parameter name  since it relates to session
- less likely to have a collission due to the _ prefix

gh-49
Add Invalid Username/Password to users sample

gh-49
Polish users log in error style
Remove dependency on Spring for MapSessionRepository
Added Hazelcast Sample

Fixes gh-63