Add the back-end support of tabs

Make backend support xml and tabs/

There are two kinds of files in tabs.
1 The tab htmls which needs to be puted as tabs in navigation bar.
2 tabs.xml which define the detail way shown the tabs.such as the
  order and the title and path.
  1) order defines the tabs order in the navigation bar.
  2) title defines the name needs be shown in navigation bar.
  3) path defines the tabs path in UI.

This patch provide allow user to visit html in tabs
and will return the static xml in tabs.

Signed-off-by: zhoumeina <zhoumein@linux.vnet.ibm.com>
Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
Add the front-end support of tabs

1) Add the tab titles in 18n.html.tmpl

2) Edit the bookmark and reload the html

3)An exmaple of tabs config tabs.xml

4) The patch series have change the tabs files from pages to pages/
tabs so need to make tabs's makefile work, this patch is working
for this purpose.

Make po work for change tabs from pages to pages/tabs

Move the tabs from pages to pages/tabs

To ensure that the tabs files are not together with other kinds
of files, we decide to move tab files to a single folder which
only contain tabs.

This is the configuration of guests, templates, storage.
And if we want to add a new tab, we can put it into pages/tabs.
and add a item in tabs.xml.
Also, we need to add the title in i18n.html.tmpl to make it have
the right translation.

5)Add a sample for plugin.
Signed-off-by: zhoumeina <zhoumein@linux.vnet.ibm.com>
Signed-off-by: Hongliang Wang <hlwang@linux.vnet.ibm.com>