XD-1616 UI: Add username/password screen

* Add Thymeleaf template
  - Configure `Gruntfile.js` to build `login.html` and copy to Thymeleaf template directory during Grunt build
* Add Spring MVC controller to handle login
* Polish login related styles in `main.less`
* Convert `spring-xd-ui` module to Java module (Spring Boot)
  - Allows for pluggable UI (`spring-xd-dirt` simply declares a dependency to the `spring-xd-ui` module)
  - Clean-up `spring-xd-ui` related tasks in `build.gradle`
  - Allows the UI (and the Thymeleaf templates) to run in isolation
  - Remove admin ui controller configuration from `/src/main/java/org/springframework/xd/dirt/rest/RestConfiguration.java`
XD-1616 Add MediaTypeRequestMatcher

* Use the `LoginUrlAuthenticationEntryPoint` for `MediaType.TEXT_HTML` requests
XD-1616 Add `AuthenticationEntryPoint`s

* Add `LoginUrlAuthenticationEntryPoint` for request with media-type `MediaType.TEXT_HTML`
* Add `BasicAuthenticationEntryPoint` for all other requests using `AnyRequestMatcher`
* Add `@ConditionalOnProperty` so configuration only applies if `security.basic.enabled` is `true`
XD-1616 Add tests

* Polishing
XD-1616 Update `.gitignore`

* Ignore `src/main/resources/public/admin-ui` from being checked in
XD-1616 Code review polishing - remove unused files
XD-1616 Due to Xerces conflict remove `neko`
XD-1616 Redirect `/admin-ui` to `/admin-ui/`

* A successful login to `/admin-ui/login` should redirect to `/admin-ui/`
XD-1616 - Code review: fix EOF issues
XD-2155 UI: Add Tooltip Directive
XD-2155 Code review changes

* Change `angular.element('.popover').hide()` to `angular.element('.popover').remove()`
* Handle `angular.element('.popover').remove()` inside the directive not the controllers
Increase logging output from spring-xd-ui

This is necessary in order to diagnose failures on specific environments
Reverting build changes and restoring output levels
Ignoring SecurityConfigurationTests

Temporary, pending investigation on CI issues
Update readme to reference 1.0.1
Remove Kafka source and docs
More Kafka removal
Revert back to 1.0.1.SNAPSHOT for second pass at release
Release version 1.0.1.RELEASE