Give utils.copy the ability to ignore files (issue 1692)
Give utils.copy the ability to ignore files (issue 1692)

This requires a significant overhaul because we want to be able to have
IGNORE_FILES apply at every level of a recursively copied directory
(e.g. the theme static directory).  Since I was overhauling it anyway
I changed it to use os.walk, which should be more efficient.

avaris/pelican,lazycoder-ru/pelican,rbarraud/pelican,Summonee/pelican,Summonee/pelican,JeremyMorgan/pelican,deanishe/pelican,Scheirle/pelican,koobs/pelican,ingwinlu/pelican,JeremyMorgan/pelican,jvehent/pelican,levanhien8/pelican,abrahamvarricatt/pelican,Rogdham/pelican,farseerfc/pelican,ls2uper/pelican,eevee/pelican,gymglish/pelican,iKevinY/pelican,Scheirle/pelican,lucasplus/pelican,TC01/pelican,gymglish/pelican,zackw/pelican,number5/pelican,Rogdham/pelican,karlcow/pelican,catdog2/pelican,alexras/pelican,51itclub/pelican,simonjj/pelican,douglaskastle/pelican,simonjj/pelican,lucasplus/pelican,karlcow/pelican,simonjj/pelican,lucasplus/pelican,jimperio/pelican,Polyconseil/pelican,koobs/pelican,GiovanniMoretti/pelican,florianjacob/pelican,florianjacob/pelican,deanishe/pelican,Polyconseil/pelican,joetboole/pelican,garbas/pelican,douglaskastle/pelican,number5/pelican,zackw/pelican,levanhien8/pelican,ehashman/pelican,Scheirle/pelican,treyhunner/pelican,iKevinY/pelican,HyperGroups/pelican,HyperGroups/pelican,ingwinlu/pelican,jimperio/pelican,Rogdham/pelican,abrahamvarricatt/pelican,abrahamvarricatt/pelican,deanishe/pelican,TC01/pelican,rbarraud/pelican,catdog2/pelican,alexras/pelican,kennethlyn/pelican,getpelican/pelican,zackw/pelican,UdeskDeveloper/pelican,UdeskDeveloper/pelican,GiovanniMoretti/pelican,getpelican/pelican,florianjacob/pelican,deved69/pelican-1,jimperio/pelican,HyperGroups/pelican,garbas/pelican,eevee/pelican,GiovanniMoretti/pelican,deved69/pelican-1,Summonee/pelican,gymglish/pelican,jvehent/pelican,kennethlyn/pelican,lazycoder-ru/pelican,catdog2/pelican,UdeskDeveloper/pelican,51itclub/pelican,TC01/pelican,avaris/pelican,joetboole/pelican,levanhien8/pelican,karlcow/pelican,treyhunner/pelican,farseerfc/pelican,treyhunner/pelican,koobs/pelican,ls2uper/pelican,ls2uper/pelican,talha131/pelican,alexras/pelican,rbarraud/pelican,talha131/pelican,joetboole/pelican,ehashman/pelican,51itclub/pelican,lazycoder-ru/pelican,eevee/pelican,kennethlyn/pelican,number5/pelican,douglaskastle/pelican,JeremyMorgan/pelican,ehashman/pelican,garbas/pelican,deved69/pelican-1,jvehent/pelican