Move search indexing/re-indexing to the sysadmin section

OME-DCO-1.1-Signed-off-by: Sebastien Besson <seb.besson@gmail.com> (github: sbesson)
Improve re-indexing title style and add sub-titles

OME-DCO-1.1-Signed-off-by: Sebastien Besson <seb.besson@gmail.com> (github: sbesson)
Add table for re-indexing time of production servers

OME-DCO-1.1-Signed-off-by: Sebastien Besson <seb.besson@gmail.com> (github: sbesson)