Cleanup after merging code from pull request.

Wrapped bodies of functions that require spatial analyst into try-except(ImportError) statements so users who don't have spatial analyst can use arcapi (sa-dependednt functions will return 'Module arcpy.sa not found').
If we get more sa-dependent code we might consider splitting it somehow, no need to worry now.
Functions should start with lower case: ConvertMetersToFeet -> convertMetersToFeet