Replace "reccommended" with "recommended" in the "Getting started" section of the documentation

[Paolo Brandoli]

Replace "reccommended" with "recommended" in the "Getting started" section of the documentation.

Additionally,

:cpp:member:dicomhero::DataSet::ModalityVOILUT

should be replaced by

:cpp:class:dicomhero::ModalityVOILUT

‌

[Paolo Brandoli]

Addresses #159. Fixed documentation in "Retrieve image".

→ <<cset b8b016a1e802>>

[Paolo Brandoli]

Addresses #159. Updated changes log.

→ <<cset 3d416757260f>>

[Paolo Brandoli]

Resolves #159 (Fix documentation in "Retrieve Image") as per SOP FIXBUG/2

→ <<cset ca79e078443b>>

[Paolo Brandoli]

Opening 6.0.0.0 Closes #159, #290, #326, #339, #340, #347, #350, #355, #357, #358, #359, #360, #361, #362, #363, #364, #366, #367, #368, #369, #370, #371, #372

→ <<cset 41c6182f3c2d>>