math/R-DBI: Update to 0.7

Notable changes since 0.3.1:
- dbGetInfo() gains a default method.
- New generic dbBind() for binding values to a parameterised query.
- DBI gains a number of SQL generation functions.
- dbDataType() maps character values to "TEXT" by default.
- The default implementation of dbQuoteString() doesn窶冲 call
  encodeString() anymore.
- Deprecated dbDriver() and dbUnloadDriver().
- Import updated specs from DBItest.
- Require R>=3.0.0.

(minskim)