refs #2667: Create calls content type
refs #2668: Write tests for calls content type
refs #2667: Write Calls content type migration class
refs #2667: Map Calls migration
refs #2668: Fix a bug with a test, where the test would look for the value in LANGUAGE_NONE instead of the node language
refs #2667: Update files supported extensions
Changed .gitignore to accept .zip files, for test purposes
refs #2668: Add test .zip files
Made gitignore to ignore .zip files that are not in the test/export/*/file/ directories
Merge pull request #106 from razvan-tache/task_2667_2668

refs #2667, #2668 Calls content type, migration tests, migration