Context and Sandbox widget: preliminary tests to fully seperate global instances of Builder, Cache, etc. Right now, only Builder is tested.
sandbox: enhance sandbox separation, and add ExceptionManager into the sandbox management too.
sandbox: add a little comment for explaining the example
wip sandbox with clock
sandbox: ensure the container is created, and fix clock
Sandbox-clock fixed
Commit
Remove the kivy garden scripts from the main repo.
Fixed angle end and start with new fast circ alg

The problem related to the old (slow) algorithm using the absolute value
of the angle change, whereas the new one depends on the sign.
Add garden as a dependency for kivy.
Fixed texture cropping for new circle drawing alg.
Add config option to disable exiting when escape is hit.
ignore PyCharm project settings
preserve Windows friendly line endings
restore Python version on exit
include info for Python Launcher
Merge branch 'master' of https://github.com/kivy/kivy into Windows_friendly
document use of Python launcher for Windows
double-click friendly demos
Merge branch 'master' of https://github.com/kivy/kivy into use_launcher_for_windows