Cache exported plugins for performance and environmental impact

[iandunn]

Running a report against the same slug+tag n times results in it being downloaded n times, rather than once.

> ls -l /tmp/

drwxr-xr-x  8 iandunn wheel 256 Apr  2 11:33 plugin-compassionate-comments51vcFw
drwxr-xr-x  8 iandunn wheel 256 Apr  2 11:34 plugin-compassionate-commentsE8ZPVm
drwxr-xr-x  8 iandunn wheel 256 Apr  2 11:34 plugin-compassionate-commentsG57Hw1
drwxr-xr-x  8 iandunn wheel 256 Apr  2 11:31 plugin-compassionate-commentsRE6kU5
drwxr-xr-x  8 iandunn wheel 256 Apr  2 11:32 plugin-compassionate-commentsYZemwM
drwxr-xr-x  8 iandunn wheel 256 Apr  2 11:33 plugin-compassionate-commentscBHN8c
drwxr-xr-x  8 iandunn wheel 256 Apr  2 11:31 plugin-compassionate-commentsonAsnl
drwxr-xr-x 12 iandunn wheel 384 Apr  2 11:30 plugin-quick-navigation-interface1W1BR9
drwxr-xr-x 12 iandunn wheel 384 Apr  2 11:07 plugin-quick-navigation-interfaceCtRTsw
drwxr-xr-x 12 iandunn wheel 384 Apr  2 11:34 plugin-quick-navigation-interfaceDcAKMl
drwxr-xr-x 12 iandunn wheel 384 Apr  2 11:34 plugin-quick-navigation-interfaceKCqXqF
drwxr-xr-x 12 iandunn wheel 384 Apr  2 11:28 plugin-quick-navigation-interfacea10S2Y
drwxr-xr-x 12 iandunn wheel 384 Apr  2 11:33 plugin-quick-navigation-interfacecn14AE
drwxr-xr-x 12 iandunn wheel 384 Apr  2 11:29 plugin-quick-navigation-interfacegws2BZ
drwxr-xr-x 12 iandunn wheel 384 Apr  2 11:23 plugin-quick-navigation-interfacekI1SMv
drwxr-xr-x 12 iandunn wheel 384 Apr  2 11:29 plugin-quick-navigation-interfaceoaLNtO
drwxr-xr-x 12 iandunn wheel 384 Apr  2 11:33 plugin-quick-navigation-interfacevNaVOw

For small plugins on a fast connection, that's not a problem. It could be a performance issue, though, and it uses more energy than needed. I'd be faster and more environmentally-friendly if the download was cached and reused on subsequent scans.

The folder could be named {slug}-{tag} instead of {slug}-{random string}.