Details: Show images.

Details: Show images.

        * src/main/java/org/glom/web/server/OnlineGlomServiceImpl.java:
Move some code into
        * src/main/java/org/glom/web/server/ConfiguredDocumentSet.java:
so it can be used in:
        * src/main/java/org/glom/web/server/OnlineGlomImages.java: A new servlet just
for serving image data.
* src/main/webapp/WEB-INF/web.xml: Mention the new servlet.

* src/main/java/org/glom/web/shared/DataItem.java: Added get/setImageDataUrl().
        * src/main/java/org/glom/web/client/ui/details/DetailsCell.java:
setData(): For image field types, add a GWT Image widget,
with the URL that was set in the DataItem.

        * pom.xml: Depend on org.apache.httpcomponents for UriBuilder.
        * src/main/java/org/glom/web/server/database/DBAccess.java:
        convertResultSetToDTO(): Set the URL for image data, so the client browser
can retrieve the image from our new servlet. This uses UriBuilder.
Move getPrimaryKeyField to:
 * src/main/java/org/glom/web/server/libglom/Document.java:
Added getTablePrimaryKeyField().

        * src/main/java/org/glom/web/server/database/DetailsDBAccess.java:
        * src/main/java/org/glom/web/server/database/ListDBAccess.java:
        * src/main/java/org/glom/web/server/database/RelatedListNavigation.java:
        Adapted.