Cleaned up various fragments and fixed a compilation error that occured when switching metric container.

Fixed a wrapping problem in the ETX EWMA calculation.

Corrected the multiplier of the link metric, and simplified the configuration
so that the user does not need to specify the multiplier.
Merge pull request #361 from nvt/rpl-mrhof-fix

MRHOF fixes
Fixed printout that used deprectated rpl_parent_t structure