Several typos

line  8 : A normal session with the processign tools  --->'processign'  should be 'processing'

line 34 : from a DEM in jut one single step ----> 'jut' should be 'just'

line 48 : Here wil have to define the input we want  ---> 'Here wil' should be 'Here we will'

line 58 : *Slope, aspect, curvatures* algorithm ---> name of the algorithm is *Slope, aspect, curvature*  'curvature' should therefore be singular

line 96 :  it anywhere you want an open it later ----. 'an' should be 'and'
Merge pull request #427 from DiGro/patch-1

Several typos