Actually debug Thingy and fix a lot of things
pathlib -> os.path, and factorize checksum calculation
use get instead of calculate for more correct semantic
Small unimportant update to core module
Fix: after abandon pathlib, we need to use os module
Complete thingy checksum functions
Add a validity check function. the baseline approach is to check file size >0
Fix a problem where mal-formed json file will cause a crash
Rework Tasky
Make a more convenient way to track files in Thingy
Rename to make the naming more consistent
Make multiple-input mode possible. Also delete a debug message
Improve Boardy to have some default environments
Add some callback mechanism for scheduler