Improvements to the drawing logic

This update completely reworks the entire drawing logic and should lead
to significant 3-7x speed improvements in animations and reduce the
idle CPU load on a not too busy bar to a level that is barely noticeable.

Improvements and Additions

• Significant performance improvements in all use cases, but especially in
  animations

• popup.background.image can now be used and the items are aligned
  accordingly, e.g. see this Spotify widget, where I have the album art below
  the controls in a popup:
  

• popup.background.shadow is handled properly now.

• New mouse.entered.global and mouse.exited.global events

• Better error messages for all configuration commands

• Add -fno-common flag for compilation to fix problems with new compiler standards

• Key-frame support for animations: https://felixkratz.github.io/SketchyBar/config/animations#perform-multiple-animations-chained-together

• Add notch_offset and notch_width options to --bar domain,
  along with positions q = left of the notch and e = right of the notch to properly
  account for notched internal displays

• New animation function: quadratic

Fixes

• Fixes a slight memory leak when querying default_menu_items

• Fixes a crash when an NSDistributedNotificationCenter event would not sent a proper JSON object

• Major Performance Optimizations by @FelixKratz in #191
  Full Changelog: v2.6.0...v2.7.0