Fix problems to open plugin's help pages

Kimchi is currently not able to configure and open help pages of any
plugin tab. This patch fixes this problem and removes the HELP button
if any Kimchi tab or plugin tab do not have a help configured properly
for the language being used.
(eg. if plugins/<tab_html>/help/<lang>/<tab_html>.html does not exist,
then the help button is disabled).

A help page for a plugin tab follow same Kimchi system:
   - html help file should have the same name of plugin html tab file;
   - html files should be placed in plugin's " ui/pages/help/<LANG> "
     path;
   - plugin should add following lines to <PLUGIN_NAME>.conf:
        * [/help]
        * tools.staticdir.on = True
        * tools.nocache.on = True
        * tools.staticdir.dir = '<HELP PAGE DIRECTORY>'

Signed-off-by: Rodrigo Trujillo <rodrigo.trujillo@linux.vnet.ibm.com>
Changes in sample plugin to fix and improve help

This patch set changes the Sample plugin, adding a new tab, modifying
naming and other elements in order to show help pages properly.

Signed-off-by: Rodrigo Trujillo <rodrigo.trujillo@linux.vnet.ibm.com>