main/postmarketos-ui-kodi: fix startup and missing dependencies

fixes the desktop file:

• add -- to make cage ignore kodi's arguments
• add --standalone to kodi's arguments

update the dependencies:

• add upower as kodi tries to communicate with it to read battery status
• add pulseaudio as kodi complains it is missing
• add elogind as it is required for cage to run
• remove xorg-server

Fixes #469 (closed)