[pve-devel] Online Help for complex PVE panels V2

[Emmanuel Kasper]

Changes since V1:
 * the help button was not hidden after switching InputPanels via
 direct tab clicks. To solve this, add a listener for 'deactivate' events,
 and react appropriately (1/5) Since the pve Wizard sends this event in all cases,
 remove the call to hide() in the wizard (2/5)
 * add in the pveHelpButton documentation header that this button is
 meant for modal windows. Components located in the workspace area
 can simply add a Standard ExtJS button in their toolbar if they want a help button
 in the future (1/5)