More refactoring: (1) Moving all widgets in the main library client.ui to be ComplexWidgets and be containers rather then elements from client.ui.html (2) Making ListItem be a list item and creating an AnchorListItem (3) Removal of the confusing HasHTML/HasText interfaces

Conflicts:
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/Alert.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/Anchor.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/AnchorListItem.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/Badge.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/HasTarget.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/HasToggle.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/Heading.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/ListItem.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/Pagination.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/PanelHeader.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/TabListItem.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/base/AbstractAnchorListItem.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/base/mixin/TextMixin.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/html/OrderedList.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/html/Paragraph.java
	gwtbootstrap3/src/main/java/org/gwtbootstrap3/client/ui/html/Span.java