[ModalCloseButton] Rework ModalCloseButton to be Ajax based
Issue #451 - Use AjaxCallListener#onBeforeSend() to set the new location.hash.

This way the application may make its own ModalCloseButton that operates completely on the client side by using AjaxCallListener#onPrecondition("return false;")
Use wicket-webjars 0.4.4
[bootlint] Update Bootlint to 0.7.0. Run the linter manually as explained at https://github.com/twbs/bootlint/issues/171#issuecomment-62070774
[bootlint] Add a singleton instance of BootlintHeaderItem
Fixes #450 - Add ITheme#getResourceReferences() method to be able to depend on the theme and allow lazy initialization of Webjars resources
Issue #442 - Add Bootstrap Material Design theme
Issue #442, #450 Rework #450 to allow depending on any HeaderItem. This way MaterialDesignTheme can initialize itself ondomready
Issue #442 - Add a shell script to download the last available resources from the dist/ folder
Issue #442 - Improve the samples markup
Issue #442 - Improve the markup of FileInput sample
Issue #442 - Optimize imports
[bootlint] Update Bootlint to 0.8.0
Issue #442 - Revert to Flatly as a default theme for the samples
Merge pull request #463 from l0rdn1kk0n/442-material-design

442 material design
Merge pull request #451 from l0rdn1kk0n/90-ModalCloseButton-anchor-with-Ajax

[ModalCloseButton] Rework ModalCloseButton to be Ajax based
Fixes #465 - Update Bootstrap to 3.3.1
Update Modernizr to 2.8.3
Update the expectation of a test after the upgrade of Bootstrap to 3.3.1
Update Wicket to 6.18.0