Make the package install code aware of the NSB target version [WIP]

[Work in progress]

Use (for now) the solution-level property indicating which major version of NSB to target, and install nuget packages accordingly. The logic is as follows:
* For NSB v5, use the latest for all packages + the ServiceContro.Plugins.Nsb5.* packages.
* For NSB v4 use the latest version for the current major version for all packages (e.g. 4 for the core packages, 5 for the azure transport packages, and 1 for RabbitMQ and SQL transports) + the ServiceContro.Plugins.Nsb4.* packages. Figuring out what the latest is requires querying a feed directly. 

Also add support for overrides through an ini file located at %LOCALAPPDATA%\ServiceMatrix\servicematrix.ini. The current syntax for the file is:

	[Feed]
	Url=some feed url

	[Packages]
	NServiceBus=4.5.0
	NServiceBus.Interfaces=4.4.0
	NServiceBus.Autofac=4.4.0

The [Feed] section indicates a feed to use to override both the configured feeds for nuget but also the default feed url used to query the latest version for a given major. The [Packages] section is used to override the version for a specific package, taking precedence over everything else.

Also addressed most R# warnings on modified files.