File class members are encapsulated, and internal lock was added.

A lock was added to the file class to properly handle multiple threads accessing the self encryptor. Actual chunk storage and incrementing is still a work in progress.

This technically completes JIRA ticket MAID-153 too.
Ah right, we can get rid of this, as it was basically a no-op (create a temporary directory and check if it is a directory.)