Fix missing examples repo

Move examples to https://github.com/beagleboard/cloud9-examples

pru: missed adding write_init_pins.sh

pru examples: added init_pins support

Add PRU examples

* Integrated so that you can press the "RUN" button in Cloud9 IDE
* Tested with Linux beaglebone 4.9.82-ti-r102
* Assumes /lib/firmware/AM335X-PRU-RPROC-4-9-TI-00A0.dtbo overlay is loaded

Merge branch 'add-pocketbeagle-examples' into gh-pages

Makefile: fix files stored in /var/lib/cloud9

Makefile: create /var/lib/cloud9

Makefile: work without htmlproofer

Fixes for Debian packaging