Better instruct for practice 1 based on feedback

Added a data section. Put instructions and questions that should be
asked after each task. Forget about flight lines file and make
topography extra.
Merge branch 'master' into pratica1
Ask about colormap in world grav task
Merge branch 'master' into pratica1
Merge branch 'master' into pratica1
Merge pull request #3 from leouieda/pratica1

Melhora nas intruções baseado na aula de quarta