New Makefile and scripts for vault/

The same framework as that in Minthril/ is now used to compile an
individual question. Morever, all 4 versions of a question are compiled in one go.
Previews for each version [0-3] are available in their individual folder

TODO: BlockDBSlots should create links to common/makefile/vault.mk and
common/scripts/compile.sh within the newly created folder

Old makefiles - individual.mk - and template TeX files can be removed
Merge pull request #486 from abhinavc/master

New Makefile and scripts for vault/