Added OSM copyright string

Moved strings from code to the English and German strings.xml files.
Added a comment to the layout file of the map about where to find the
code that sets the strings.
Fix misspellings
Merge pull request #1296 from AngelFQC/patch-1

@AngelFQC Fix misspellings in ES translation
Merge pull request #1273 from Djfe/Add-OSM-string

@djfe Translatable OSM copyright string #1264