remove named binary

[HLFH]

The named binary is a duplicate of the trust-dns binary.
They both take the same path src/named.rs.

People may think having a named binary offers a drop-in replacement with BIND.
But at the same time, it conflicts with BIND and the named binary.
I think Trust-DNS provides enough compatibility by itself with BIND but does not need to provide as well a named binary.

Some users may have installed on their system both BIND and Trust-DNS.
They may want to use or try both for some reasons.
Or they may use BIND only for BIND utilities such as dig, host and nslookup.
On Arch Linux, BIND and the BIND utilities are part of the same package.
And overwriting the named binary would just create an unnecessary conflict.
For example, PowerDNS, another BIND alternative, does not conflict with BIND because it does not provide a named binary.
Trust-DNS is a great brand in the making, and I believe we should promote more the use of the trust-dns binary.

[bluejekyll]

I left this in place as a backward compatible option since it was the original name that I had (probably poorly) chosen. I think it's been long enough that we can make the change without concern.

[HLFH]

I have just removed the "## DEPRECATED" comment. I think it was for the removed named binary, so I guess this comment is no longer needed.

I have also set target/debug/named to target/debug/trust-dns to avoid issues with the testing suite.

[bluejekyll]

Thanks for the PR!