added script for testing of differnt timestamp ranges

added class to extract a list of valid metadata from the toar database
added testscript for this class

added notebook to use this new class to extract data for all stations between 2000 and 2018.

-changed from one large request to yearly requests
-changed waiting time for individual requests
-cleaned up

toar_rest_client:
-added function to alter the waiting intervals before checking for the results
-added indention to cache file
-worked on debug output
-

extraction of 19 years is no spilt into several requests covering one year each.

worked on README
- added syntax highlighting to code snippets
- reworked information on examples
- added some links and now hiding urls
- added tested OS

added some typing for return values in rest toar_rest_client
added flag to control debug output by toar_rest_client; Default: False

added some documentation to notebook

added type_of_area for separation of stations

split into usage of optional parameters and an example without a restriction, that will run for several days.

enabled execution with additional query parameters

added some error handling when using a cahced endpoint

under development

added comments to produce_data example