Syntax Warnings enmapboxprocessing

[Benjamin Jakimow]

Some SyntaxWarnings are shown during EnMAP-Box start. Probably easy to remove

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C:\Users\geo_beja\Repositories\enmap-box\enmapboxprocessing\algorithm\appendenviheadertogtiffrasteralgorithm.py:60: SyntaxWarning: "is not" with a literal. Did you mean "!="?
  if fwhm[0] is not 'None':
C:\Users\geo_beja\Repositories\enmap-box\enmapboxprocessing\algorithm\appendenviheadertogtiffrasteralgorithm.py:62: SyntaxWarning: "is not" with a literal. Did you mean "!="?
  if bbl[0] is not 'None':

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[Andreas Janz]

resolves #756

→ <<cset faf43c4d1aa3>>