Fix content issues in TTN tutorial

Fix missing line breaks

Update cover image for flash tutorials

Update micro trace link in Lauterbach tutorial

Remove confusing wording about license validity

Rephrase haar cascade explanation

Another try to fix the download link for the pbm file

Rephrase abstract of face detection tutorial

Openmv text improvements (#48)

* Add a sentence after quote from OpenMV

* Add troubleshooting improvements

* Clarify on the flashing process

* Fix incorrect pixel calculation

* Update the OpenMV download links

Code typo (#47)