Adds --skip=image_resize to 'wp import' command.
Adds --skip=image_resize to 'wp import' command.

Gives import user the option to skip image thumbnail generation during
image attachment import. Image resizing is extremely CPU intensive and
makes imports run much slower, especially during test runs that don't
necessarily require all image sizes. Image resizing can always be
deferred post import by running the 'wp media regenerate' command.

xwp/wp-cli,gedex/wp-cli,staylor/wp-cli,2ndkauboy/wp-cli,shawnhooper/wp-cli,Yas3r/wp-cli,rodrigoprimo/wp-cli,borekb/wp-cli,Yas3r/wp-cli,xwp/wp-cli,dpq/wp-cli,duncanjbrown/wp-cli,rohmann/wp-cli,anttiviljami/wp-cli,shawnhooper/wp-cli,nyordanov/wp-cli,boonebgorges/wp-cli,a7127cff69cab32e5c4723e8446e21c4b7325dc/wp-cli,rodrigoprimo/wp-cli,Yas3r/wp-cli,nyordanov/wp-cli,gedex/wp-cli,miya0001/wp-cli,aaemnnosttv/wp-cli,blueblazeassociates/wp-cli,ahmadawais/wp-cli,anttiviljami/wp-cli,rohmann/wp-cli,rodrigoprimo/wp-cli,GaryJones/wp-cli,gitlost/wp-cli,GaryJones/wp-cli,blueblazeassociates/wp-cli,staylor/wp-cli,shawnhooper/wp-cli,duncanjbrown/wp-cli,trepmal/wp-cli,borekb/wp-cli,here/wp-cli,pressednet/wp-cli,here/wp-cli,aaemnnosttv/wp-cli,a7127cff69cab32e5c4723e8446e21c4b7325dc/wp-cli,spiritedmedia/wp-cli,duncanjbrown/wp-cli,ahmadawais/wp-cli,boonebgorges/wp-cli,dpq/wp-cli,trepmal/wp-cli,pressednet/wp-cli,nyordanov/wp-cli,anttiviljami/wp-cli,JohnDittmar/wp-cli,2ndkauboy/wp-cli,GaryJones/wp-cli,macbookandrew/wp-cli,gitlost/wp-cli,ahmadawais/wp-cli,a7127cff69cab32e5c4723e8446e21c4b7325dc/wp-cli,spiritedmedia/wp-cli,heiglandreas/wp-cli,JohnDittmar/wp-cli,spiritedmedia/wp-cli,JohnDittmar/wp-cli,pressednet/wp-cli,borekb/wp-cli,heiglandreas/wp-cli,dpq/wp-cli,boonebgorges/wp-cli,xwp/wp-cli,macbookandrew/wp-cli,miya0001/wp-cli,staylor/wp-cli,rohmann/wp-cli,aaemnnosttv/wp-cli,gitlost/wp-cli,blueblazeassociates/wp-cli,2ndkauboy/wp-cli,macbookandrew/wp-cli,gedex/wp-cli,trepmal/wp-cli,miya0001/wp-cli