Update README.md

Adds a retry loop for applying updates because the updating flag in BaseX sometimes doesn't delete correctly on the first try (not sure why, though I suspect it has something to do with the IKVM abstraction layer for the filesystem and timing of the initial lock file creation).

Fixes a problem with Node.Equals() for invalid nodes. Also adds NUnit using NuGet (rather than requiring it to already be installed in the GAC).

Merge remote-tracking branch 'origin/master'

Initial commit

Some small fixes, mainly to avoid problems due to edge cases during updates.

Several bug fixes to persistence framework.

Adds some new global persistent collection classes.

Persistent collections now reuse existing collection instances if possible.

Adds a much better way of getting non-member-based persistent dictionaries and lists. This required some behind the scenes changes to the way types and member information is passed around, but all works well now.

Better support for custom TypeConverters in persistence framework.

Adds a little error handling for the custom persistent object initializer.

Removed the CustomPersister and instead added the custom persistence interfaces to the DefaultPersister allowing for custom behavior with or without the default persistence attributes. Also added a custom initialize interface that lets implementors execute custom code after construction and after members are fetched (since the default constructor is executed before members are fetched).

Adds support for custom and explicit TypeConverters in the default persister.

Adds a couple new properties (like AutoFlush).