GLPI 0.84 compatibility
Makes plugin compatible with GLPI 0.84Applied changes as documented in GLPI Plugins wiki to make it compatible with GLPI 0.84 code.
- Previous tabs management (based on "headings*" hooks) was removed (change initiated with GLPI 0.83 release): Removed "ajax/connection.tabs.php" which is not needed anymore.
- getPlural() function changed and don't support tables in "...ed" anymore (eg. "glpi_plugin_connections_connectionratesguaranteed"): The corresponding item was renamed to PluginConnectionsGuaranteedConnectionRate so were the depending files/classes (dropdown, front, etc.). This name is also more english (adjectives before noun).
- No need to define GLPI_ROOT constant anymore
- Some methods/functions had changed names/location/prototype: adapted plugin to take this into account.
- Translation now uses the __() method: Migrated $LANG uses for non-plugin texts
- Use Toolbox::decodeArrayFromInput() when trying to filter out already used/linked items from dropdown
- Fixed a missing locale for Rights management (not sure if it wasn't already broken in 1.6.3).
Sets plugin version to 1.6.4.