* compiler: rename vget to tools/vpm, implement draft support for v vpm search, v vpm update, v vpm install, v vpm remove, v vpm help .
* compiler: use "v pm" instead of "v vpm" to reduce the redundancy of typing, as suggested by slapden
* Use 'v install modulename', 'v search keywords', 'v update modulename', 'v remove modulename' instead of the longer 'v pm install modulename' etc.
