Convert all GRASS 6 vector maps to GRASS 7

Convert automatically all GRASS 6 vector maps to GRASS 7 (including attribute transfer from DBF to SQLite)

To become usable in GRASS 7, all vector maps in a mapset need to be updated to the improved vector file format and database management.

Run this in GRASS 7:

# first rebuild topology
v.build.all

# set new default db connection (to SQLite default)
db.connect -d

# copy attribute tables from old db to new db, delete old tables in DBF format
v.db.reconnect.all -cd