Remove Zac Gordon's register-block-type and examples

[bobbingwide]

The example blocks in the blocks\register-block-type and blocks\examples folders have served their purpose and have helped me to start building my own blocks. They have already been removed from the blocks that I've been building, so the source files can now be removed.

register-block-type first

[bobbingwide]

For delivery we need to change the target directory of the build from assets to blocks/build.
This makes it consistent with the Gutenberg plugin and with the oik-zip plugin which packages the files for delivery. oik-zip doesn't package files in the assets folder.