Add i18n to messages.

Add a message source in order to internationalize the application.
Add custom CSS stylesheet

Add a custom CSS stylesheet and the header banner image.
Sidebar style

Apply style to sidebar.
Maven jetty plugin configuration
CSS styling

Align CSS layout with the design.
Some more styling
Fixing vertical button gradient
Merge pull request #2 from juanluisrp/page-structure

Page structure and style
Form layout and styling.

Form layout and styling. Also add datetimepicker and multiselect
Bootstrap plugins.
Fix collapsible panel arrow indicator

Fix the arrow of the collapsible panels. When the panel is closed there
is a down arrow and when it is opened there is an up arrow.
Merge pull request #3 from juanluisrp/page-structure

Form layout and styling