openage v0.5.3 release

@heinezen

Fixes a bunch of small errors and removes a lot of legacy code, making the engine easier to build.

Also, the dependencies SDL2 and SDL2_Image are no longer required!

What's Changed

Fix version tag regex failure when HEAD is tagged by @heinezen in #1583
doc: Fix typos in converter by @fabiobarkoski in #1588
Remove dangling refs in modpack info load by @heinezen in #1589
Neutralize remaining instances of gendered language by @leetfin in #1590
Fix typos by @zoli111 in #1593
Temporary file/directory creation by @Ashhar-24 in #1594
Converter debug by @fabiobarkoski in #1591
Fix append mode not available by @heinezen in #1595
Check OpenGL format correctly on Wayland by @heinezen in #1597
Dynamically fetch default FBO by @heinezen in #1598
Add atan2 to FixedPoint by @askastitva in #1587
Mirror anchor offset when flipping is active by @heinezen in #1600
PR templates by @heinezen in #1599
Use block indent for aligning after open brackets by @heinezen in #1602
complete if-else branch to fix pylint error by @AyiStar in #1604
Make 'main' the default entrypoint by @heinezen in #1606
Revert "Merge pull request #1602 from heinezen/clang-format-align" by @heinezen in #1605
Add math constants corresbonding to util/math_constants.h for FixedPoint by @AyiStar in #1607
Add setuptools as conditionl dependency by @heinezen in #1610
Remove legacy subsystem code by @heinezen in #1550
Changelog release 0.5.3 by @heinezen in #1611

Full Changelog: v0.5.2...v0.5.3