Change the date-fields from string to DateTime

[TopperDEL]

Within the Models there are some Date-Fields like "Created" on a file - they are strings currently as they are provided as strings from the Java-libstorj-library. Convert them to DateTime for better .Net-Usability.

[kaloyan-raev]

@TopperDEL I'd appreciate if you open issues like this also in the java-libstorj project.

[TopperDEL]

You're right, sorry. Maybe this is the better place for this as the Java-consumers would like to have "real Dates", too. True. Will do this - then my wrapper can consume them natively.

[TopperDEL]

Opened an issue for this in java-libstorj