GoodData Writer now uses Project Model API

All newly created writers will use GoodData's Project Model API by default (also known as LDM API). Existing projects still use the CL tool but will be switched in near future.

New writers also don't use date facts in datasets referencing date dimensions (this does not apply for time dimensions). Counting without Date facts is covered by "Date Attribute Arithmetic". Older projects have reports built upon these facts and can't be switched automatically so far.