Update imagePath to prefer theme, then app, then core images
Update imagePath to prefer theme, then app, then core images

imagePath updated so that image searches follow this priority:

1) /themes/$theme/apps/$app/img
2) /themes/$theme/$app/img
3) /themes/$theme/core/img
4) $appPath/img
5) /$app/img
6) /core/img

For each folder:
- if the specified file exists, use it.
- otherwise, if $basename.svg does NOT exist, try $basename.png
(This might better be "if filename was an svg, try the png"...)

sharidas/core,pollopolea/core,pmattern/server,jbicha/server,Ardinis/server,owncloud/core,michaelletzgus/nextcloud-server,nextcloud/server,IljaN/core,nextcloud/server,michaelletzgus/nextcloud-server,bluelml/core,cernbox/core,xx621998xx/server,andreas-p/nextcloud-server,pixelipo/server,pixelipo/server,Ardinis/server,owncloud/core,pmattern/server,IljaN/core,endsguy/server,IljaN/core,pmattern/server,bluelml/core,Ardinis/server,phil-davis/core,pollopolea/core,whitekiba/server,pixelipo/server,cernbox/core,nextcloud/server,whitekiba/server,sharidas/core,xx621998xx/server,bluelml/core,andreas-p/nextcloud-server,sharidas/core,andreas-p/nextcloud-server,sharidas/core,pixelipo/server,whitekiba/server,jbicha/server,michaelletzgus/nextcloud-server,jbicha/server,Ardinis/server,pollopolea/core,cernbox/core,bluelml/core,xx621998xx/server,pmattern/server,whitekiba/server,Ardinis/server,andreas-p/nextcloud-server,cernbox/core,sharidas/core,endsguy/server,bluelml/core,jbicha/server,pmattern/server,jbicha/server,whitekiba/server,IljaN/core,owncloud/core,michaelletzgus/nextcloud-server,andreas-p/nextcloud-server,xx621998xx/server,owncloud/core,nextcloud/server,owncloud/core,endsguy/server,pollopolea/core,pixelipo/server,cernbox/core,endsguy/server,xx621998xx/server,endsguy/server,pollopolea/core,IljaN/core