[WIP] More sharing attribute config by reference optimizations

Centered around avoiding repeated calls to State.get, across method
boundaries, by passing an already retrieved attribute cfg across
private method calls.

Mainly targets get()/set() operations.

attribute, base, dd, widget, app tests all pass

This commit (Chrome 24):

MyBaseCore with 10 simple value attributes - get x 7,769,862 ops/sec ±1.37% (91 runs sampled)
MyBaseCore with 10 simple value attributes - set x 2,027,186 ops/sec ±2.37% (86 runs sampled)

MyBaseCore with 20 varied attributes (using perf. best practices) x 25,421 ops/sec ±1.33% (94 runs sampled)
MyBaseCore with 20 varied attributes x 9,060 ops/sec ±6.35% (59 runs sampled)
MyBaseCore with 10 simple value attributes x 54,249 ops/sec ±1.23% (94 runs sampled)
MyBaseCore x 163,314 ops/sec ±1.49% (91 runs sampled)
BaseCore x 174,555 ops/sec ±1.08% (94 runs sampled)

Prior commit (Chrome 24):

MyBaseCore with 10 simple value attributes - get x 2,475,836 ops/sec ±0.31% (96 runs sampled)
MyBaseCore with 10 simple value attributes - set x 1,077,515 ops/sec ±0.24% (96 runs sampled)

MyBaseCore with 20 varied attributes (using perf. best practices) x 25,250 ops/sec ±1.24% (95 runs sampled)
MyBaseCore with 20 varied attributes x 9,442 ops/sec ±6.42% (62 runs sampled)
MyBaseCore with 10 simple value attributes x 54,512 ops/sec ±0.43% (93 runs sampled)
MyBaseCore x 149,460 ops/sec ±0.83% (92 runs sampled)
BaseCore x 158,574 ops/sec ±0.93% (93 runs sampled)

3.8.0 (Chrome 24):

MyBaseCore with 10 simple value attributes - get x 2,436,501 ops/sec ±1.34% (87 runs sampled)
MyBaseCore with 10 simple value attributes - set x 589,829 ops/sec ±1.01% (94 runs sampled)

MyBaseCore with 20 varied attributes (using perf. best practices) x 12,753 ops/sec ±1.37% (92 runs sampled)
MyBaseCore with 20 varied attributes x 6,644 ops/sec ±4.20% (70 runs sampled)
MyBaseCore with 10 simple value attributes x 22,942 ops/sec ±0.44% (92 runs sampled)
MyBaseCore x 57,039 ops/sec ±1.37% (91 runs sampled)
BaseCore x 61,830 ops/sec ±1.21% (91 runs sampled)