Restructure blocks with a "master" and multiple functional blocks

[sconklin]

Restructure so that there's a "master" block with configuration information such as radio serial number, etc, and separate blocks for rx audio source (existing), and (future) tx audio sink, IQ source and sink, etc

[dkozel]

The two implementational details I can think of here are:

1. Having the individual functional blocks use the same underlying control access per radio
2. Supporting having more than one FlexRadio Device block and being able to associate each functional block with a specific FlexRadio. Serial number is probably the (a?) useful key.