Initial functionality, tests and everything else.
Some random change accidentally left out.
Test credentials are now stored externally

Mega test account credentials are now stored in two files:
Mega_Account.txt and Mega_Password.txt in My Documents. Kind of silly,
but a useful temporary measure to avoid putting the credentials in the
repo.
Added NuGet package creation scripts.

Also updated immutable collections package to latest beta, since there
were some conflicts with existing one.
Typo fix