ENG-6647: Fixes to SQLCommand: - Just use java null for null - Add support for @UpdateClasses - Handle null filenames for @UpdateApplicationCatalog and   @UpdateClasses correctly
ENG-6647: Fixes to SQLCommand:
- Just use java null for null
- Add support for @UpdateClasses
- Handle null filenames for @UpdateApplicationCatalog and
  @UpdateClasses correctly

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