* Root folder variable names are now more descriptive
* clone_repo() now restores the current working directory
* Removed setup_upstream_repo() since it's now identical to clone_repo()
* Moved am_patches()'s for loop into user scripts so the filename prefix
doesn't need to be included in every patch filename
* Renamed am_patches() to git_am() since its only job now is to run "git am"
* Removed unused apply_patches() function
* Fixed typo in git_am()'s ignore_whitespace arg name
We migrated to magic statics for lazy construction like the following:
```cpp
class Singleton {
static Singleton& GetSingleton() {
static Singleton instance;
return instance;
}
};
```
