Various changes, index.html, servlet 3.0, rename servlet.Welcome.java

1) incorporated twitter bootstrap into index.html entry point, which includes a login modal
2) changed web.xml from Servlet 2.5 to 3.0 specification
3) renamed servlet Welcome.java to Login.java since it controls login
Merge branch 'master' of github.com:ambantis/bugtracker into servlet

added twitter bootstrap functionality to entrypoint index.hmtl