Remove old legacy code

[mkg20001]

Buildozer seems to have improved greatly, thus removing the need for some hacks/workarounds as well as the forks.

list WIP

• Workaround for downloading newer SDKs/NDKs: ?
• Workaround for buildozer sometimes not properly fetching stuff: Removed
• $CI_MODE feature: Possibly get this merged upstream (Add ci_mode to disable download progress kivy/python-for-android#1727 and Add ci_mode to disable download progress kivy/python-for-android#1727)
• libjpeg fix: Merged upstream
• Consider using offical docker image, or syncing with it
• Wrapper command for docker buildozer: Update
• Makefile cleanup