Offer sparql escape helpers in line with other templates.

[cecemel]

It seems the sparql escape helpers are not in line with what is provided by other templates.
See, as golden standard, for example: https://github.com/mu-semtech/mu-javascript-template
It would be nice to have such functionalities consistent for the elixir-template

See also: mu-semtech/project#2