This commit forward ports the changes made for 0.6.17, in order to store
the type and sensitive flag against outputs.
It also refactors the logic of the import for V0 to V1 state, and
fixes up the call sites of the new format for outputs in V2 state.
Finally we fix up tests which did not previously set a state version
where one is required.
This changes the representation of maps in the interpolator from the
dotted flatmap form of a string variable named "var.variablename.key"
per map element to use native HIL maps instead.
This involves porting some of the interpolation functions in order to
keep the tests green, and adding support for map outputs.
There is one backwards incompatibility: as a result of an implementation
detail of maps, one could access an indexed map variable using the
syntax "${var.variablename.key}".
This is no longer possible - instead HIL native syntax -
"${var.variablename["key"]}" must be used. This was previously
documented, (though not heavily used) so it must be noted as a backward
compatibility issue for Terraform 0.7.
