[book] initial prop dialog
[book] continue prop dialog
[book] prop dialog except save
[book] prop dialog complete
[book] prop dialog complete
[book] integrate design menu, toolbar
[book] run multi-line command
[book] update spacefm.pot
[book] prop dlg limit built-in items
[book] prop dlg save on open in editor; move opts
[book] prop dlg layout; check terminal uncheck task
[book] prop dlg icon sens; popup task compliance
[book] prop dlg open on missing target
[book] prop dlg plugin icons; activate entries
update manual/homepage locations (github.io)
[book] prop dlg sep submenu sens
[book] prop dlg manual updated; misc adjustments
fix item prop dlg loses name icon
custom Application chooser mime context
session dont save default menu labels and icons

This will make session files smaller and will allow updated translations of
menu item names to be seen so long as the user did not change the name.

NOTE:  As a result of this change, when downgrading to older spacefm versions,
customized menu item names and icons of built-in items will be lost (custom
menu items will not be affected).