Bug fixing
Changing wchar* to char* when loading windows dll

As the sepiola project does not preload the unicode macro, the windows api expects char* instead of wchar*
Changing type of snapshot_set_ids from unordered_map to QHash
Defining and implementing cleanup slots and signals for AbstractSnapshot and DummySnapshot respectivly
Aborting whole backup process if filesystem snapshot cannot be created
Cleanup on FilesystemSnapshot failure and emit final signals
Implementing FilesystemSnapshot::cleanup method
Cleaning up FS Snapshot after backup
Implementing cleanup for ShadowCopy
Making checkCleanup a mehtod instead of a slot
Making checkCleanup a mehtod instead of a slot
Implementing ShadowCopy::checkCleanup method
No singal is sent in the DummySnapshot::checkCleanup method
Checking FS Snapshot for clenup on creation of MainModel object
In scheduling waiting for backup to finish before exit app
Adding missing brackets in EventLooper connection
Small bug fixes for snapshot cleanup in ShadowCopy
Creating and removing symlinks via WinAPI
Correctly defining WinAPI functions in shadow_copy.hh
Creating method for deleting Windows-Symlinks