Fix crossdomain requests

- add @crosdomain to all endpoints;
- make default value for 'Cross-Domain-Allow-Origin: *';
- add default allowed headers ('Accept' and 'Content-Type');
- force creation of 'OPTIONS' method on all endpoints;
Force creation of 'novanetwork' network in setup

This network is required for further servers creation.
Add tests for security group migration tasks
Remove unused import from server.py
Ensure straigh argument order for image tasks
PEP8 fix
Merge branch 'newenv-fixes'

Fixes found spinning up new development environment.
Test migrate_secgroup function
Add tests for floating ip migration flows
Minor typo in unittest
Correct secgroup tests execution
Log exceptions during reset process
Set unix fileformat for test_user
Introduce Context
Extends test_user scripts to validate flow a bit
Remove tralling white spaces
Add ability to choose plugins for migration_disk
Implement context
Add tests for server tasks
Replace src, dst with context in tests for floating ip, secgroup