Start simplification of AV handling

First steps to remove the spaghetti code.  Atomspace compiles.
AttentionValue simplifcation -- everythng compiles

Unit tests are crashing; we'll fix those next
Stupid bug fix in new code
port the examples over, as well.
AttentionValue further simplification
Merge pull request #351 from linas/master

Simplify how AttentionValue is used.