Reacting to System.ObjectModel package version change
Adds missing ConfigureAwaits
fixing escaping aliases in sql queries - we used to not escape aliases for queries, so if user created query like: context.Users.Where(user => user.Id >5), we would create invalid sql. Fix is to start quoting those for all cases, so that any variables can be safely used. CR: Andrew
Only different in your mind... (Make ForeignKey and Index APIs consistent with Property and Key APIs)

This change removes the ForeignKeys and Indexes methods in the same way that Properties and Key were removed. The nested closure pattern on the Entity methods is now used consistently.
A CollectionFixture seems the right way to start and stop the redis server
for the tests, but they are not working in Xunit at the moment so this is the
next best thing. Have added a RedisXunitTestExecutor which starts the
server in its constructor and stops it in the destructor (unfortunately
had to use that because Dispose() wasn't always called).

Also found that you _must_ have only one ConnectionMultiplexer per set of
config options - more causes multi-threading issues which means the tests
sometimes work but more often fail. So set up a static Dictionary of
config options to ConnectionMultiplexer in RedisDatabase and only create
the ConnectionMultiplexer as needed.

The Simple Tests are now running with server starting and stopping as
expected both under VS and for k test - so re-enabling the latter.
Fixed a couple of issues with tests when running with no existing databases:
- Temporary code in F1Context.CreateModel calls AddProperty which replaces an existing property with a new one, without updating the keys. That causes issues when we order properties in the DatabaseBuilder and rely on reference equality, resulting in duplicate columns. The fix is to move the code at the begining of the method so they don't get recreated.
- File not found exception about Northwind.sql because specified relative path goes up one directory too much.
Updated DbMigrator.UpdateDatabase to create the database if it doesn't exist.