Adapt region queries to work with NRAO TAP service

[jjtobin]

OK, this should be created properly.

For the moment, I just copied tapsql.py form alma and edited the _gen_pos_sql function. The remainder are unchanged for the moment.

[keflavich]

Did you also modify _gen_pos_sql? I swear I saw a version in which you had included a new tapsql.py in nrao/, but that wasn't in this commit.

[jjtobin]

I forgot to do a git add to include the file, will do a new PR.