Changes and Fixes to Rift Signature Variants

1. Changed hasEffect() override since we were overriding a deprecated
version.
2. Fixed a bug where we checked if a block could be edited before
deciding whether to change the Y coordinate of the rift to be placed.
Sometimes we would place the rift in a different block. This is the
result of sticking in support for special blocks like grass and snow
without considering the impact on surrounding code. It also contradicted
comments that specifically said special blocks were ignored...
3. Cleaned up the code for checking for special blocks.
4. Fixed a bug in loading NBT data. There were no null checks on
orientation data. If a Rift Signature or Stabilized Rift Signature had
been created in a version of DD before orientations were set up, then it
cause an exception when so much as looked at in later versions of DD.
5. Partially implemented free redirects for Stabilized Rift Signatures.
The check to determine if a redirect is being done is missing.