Merge pull request #7 from IsabellaP/develop

Develop
added package to calculate drought index
added module for managing dekadal data
Merge branch 'develop' of https://github.com/TUW-GEO/poets into develop
restructured IO package, added MODIS_LST source class
fixed bug that caused error if no data available for temporal resampling
bugfixes
bugfixes
moved shapes module to separate shape package, added option to use
custom shapefiles
bugfix