update drawing tool help (#3630)
update drawing tool help (#3630)

* update drawing tool help

add missing help descriptions of publicly available drawing tools. Also switched markdown bold characters to html bold tags

* made requested changes and fixed typos

made requested changes and fixed typos

* fixed extra :

removed extra :

* fixed added in typo

removed 'can' from one of the sentences

jelliotartz/Panoptes-Front-End,amyrebecca/Panoptes-Front-End,amyrebecca/Panoptes-Front-End,amyrebecca/Panoptes-Front-End,zooniverse/Panoptes-Front-End,jelliotartz/Panoptes-Front-End,jelliotartz/Panoptes-Front-End