Bug 11614: Untranslatable label_element_title in label management

Bug 11614: Untranslatable label_element_title in label management

This patch makes those strings translatable.
Title now depends on element, all on TT file,
removed from pl file

To test:
1. Apply the patch
2. Go to Tools > Label creator
3. Clic on Manage layouts, templates, profilesor batches,
title of currently available must show with fixed
capitalization
4. Update translation languages and check new entries
msgid "Currently available batches"
msgid "Currently available layouts"
msgid "Currently available profiles"
msgid "Currently available templates

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>