Rename the existing datafile ARRL.LIST to DXCC.LIST

[w7sst]

Summary

Rename the existing datafile ARRL.LIST to DXCC.LIST.

Motivation

As discussed in Issue #142, @K6OK communicated with ARRL and we received permission to use the DXCC list from the ARRL:

Good news -- per my phone call with ARRL, permission is granted to use DXCC.LIST under two conditions

1. MRCE does not market or imply our software is endorsed by ARRL.
2. ARRL requests that we add a header to the top of DXCC.LIST that says "Used with permission: DXCC Country List, copyright ARRL."

Later in Issue #152, @scotthibbs suggested that we rename the existing ARRL.LIST file to DXCC.LIST.

Detailed Description

• rename data file
• update ARRL.pas to open the new file
• perhaps rename ARRL.pas to DXCC.pas to be a more descriptive name for this package.

Additional context