Initial draft of the panel dash using libmenu-cache backend.
Adding xdg notification spec.
Fixing mouse focus on start button (1) and hide event on Dash (2).
Refactoring notification module:
- The amount of displayed notifications at the same time is reduced to one.
- Notifications are staked into a side panel.
Merge remote-tracking branch 'origin/core_v_0.7' into merge_branches
Fix menu button issue ( menu isn't hide wen clicked).
Fix menu button issue click fails due focus lost.