sysutils/bsdstats: Update to 7.0

• Use pkg query %n:%v:%o instead of pkg info -o “*” to get list of installed packages. This simplifies processing and accuracy of split for version numbers on the report server by not having to guess where that split is.
• Check for existence of %%PREFIX%%/etc/bsdstats.conf and if it exists, restrict ports submitted to those listed in there.
• Add a note to pkg-message.in about %%PREFIX%%/etc/bsdstats.conf
• Get rid of the LIMITED config option: LIMITED is enabled if and only if %%PREFIX%%/etc/bsdstats.conf exists.

While here, also modernize the port using option helpers.

Submitted by: scrappy
Approved by: gerald (mentor)
Differential Revision: https://reviews.freebsd.org/D24644