added ability to check if a dependency is already installed.
added ability to check if a dependency is already installed.

skcript/backup,backup/backup,zBMNForks/backup,zires/backup,McStork/backup,scalp42/backup,McStork/backup,skcript/backup,interu/backup,otzy007/backup,reedloden/backup,tian-xiaobo/backup,martincik/backup,john/backup,sferik/backup,ccoenen/backup,ccoenen/backup,bernd/backup,bernd/backup,reedloden/backup,ccoenen/backup,hiphapis/backup,scalp42/backup,bukalapak/backup,hiphapis/backup,pawelduda/backup,skcript/backup,interu/backup,backup/backup,rics3n/backup,scalp42/backup,pollosp/backup,juliancheal/backup,zBMNForks/backup,martincik/backup,backup/backup,reedloden/backup,zires/backup,otzy007/backup,rics3n/backup,rics3n/backup,hiphapis/backup,interu/backup,martincik/backup,pawelduda/backup,otzy007/backup,zBMNForks/backup,pawelduda/backup,McStork/backup,tian-xiaobo/backup,pollosp/backup,zires/backup,pollosp/backup,tian-xiaobo/backup