Added hooks to stop if invalid directory is given, and more useful error messages
Added hooks to stop if invalid directory is given, and more useful error messages

flybird119/voltdb,migue/voltdb,migue/voltdb,creative-quant/voltdb,flybird119/voltdb,paulmartel/voltdb,paulmartel/voltdb,paulmartel/voltdb,simonzhangsm/voltdb,simonzhangsm/voltdb,migue/voltdb,kumarrus/voltdb,creative-quant/voltdb,wolffcm/voltdb,VoltDB/voltdb,VoltDB/voltdb,kumarrus/voltdb,kumarrus/voltdb,zuowang/voltdb,paulmartel/voltdb,kumarrus/voltdb,flybird119/voltdb,ingted/voltdb,simonzhangsm/voltdb,ingted/voltdb,deerwalk/voltdb,kumarrus/voltdb,creative-quant/voltdb,ingted/voltdb,ingted/voltdb,creative-quant/voltdb,ingted/voltdb,migue/voltdb,zuowang/voltdb,deerwalk/voltdb,deerwalk/voltdb,migue/voltdb,simonzhangsm/voltdb,wolffcm/voltdb,paulmartel/voltdb,zuowang/voltdb,wolffcm/voltdb,deerwalk/voltdb,wolffcm/voltdb,zuowang/voltdb,wolffcm/voltdb,VoltDB/voltdb,wolffcm/voltdb,deerwalk/voltdb,VoltDB/voltdb,flybird119/voltdb,migue/voltdb,VoltDB/voltdb,zuowang/voltdb,creative-quant/voltdb,ingted/voltdb,ingted/voltdb,simonzhangsm/voltdb,flybird119/voltdb,simonzhangsm/voltdb,paulmartel/voltdb,simonzhangsm/voltdb,kumarrus/voltdb,simonzhangsm/voltdb,deerwalk/voltdb,flybird119/voltdb,zuowang/voltdb,creative-quant/voltdb,wolffcm/voltdb,zuowang/voltdb,paulmartel/voltdb,migue/voltdb,flybird119/voltdb,wolffcm/voltdb,paulmartel/voltdb,kumarrus/voltdb,VoltDB/voltdb,creative-quant/voltdb,kumarrus/voltdb,deerwalk/voltdb,flybird119/voltdb,VoltDB/voltdb,ingted/voltdb,creative-quant/voltdb,zuowang/voltdb,deerwalk/voltdb,migue/voltdb