core.text: Introduce `get_system_fonts_dir` and register the dirs at start.
This would allow one to simply specify a system font like font_name: 'Comic Sans MS'
core:Text: include kivy_data_dir/fonts to resources
core:text fix logic for getting system fonts for windows
core:_text_sdl2 fix for python3
change video example so it works when tried on an android phone
fixes #2649
unbind on_anim1_complete in Sequence
Merge pull request #2742 from merriam/master

Create app_suite demo
core:Introduce native clipboard for most target OS
core:clipboard add missing files for windows and kde target
core:clipboard. Minor optimisation.
fixes for clipboard_dbusklipper
clipboard_winctype fixes for windows
make sure platform specific clipboard implementations are preferred
core:clipboard_pygame is able to paste unicode text
Merge pull request #2739 from kived/anim-sequence-repeat

unbind on_anim1_complete in Sequence
Merge pull request #2704 from olymk2/fix/video-example-on-android

change video example so it works when tried on an android phone
Merge pull request #2743 from kivy/clipboard_os_specific

Clipboard os specific
Merge pull request #2673 from kivy/system_fonts

System fonts
Merge pull request #2746 from merriam/master

Convert print statements to print function
doc: moved addition note to the corresponding property