Merge pull request #1171 from ruudkobes/master

Fix documentation for OrderItem getter/setter
Order taxons with hierarchy in mind.
Merge pull request #1173 from kayue/patch-12

Order taxons with hierarchy in mind.
Move from preUpdate to onFlush

preUpdate event is actually not able to change relation, which is our
case with new InventoryUnit in relation with OrderItem. PreFlush allows
that.
Add expression language to ParametersParser
Remove unused functions
Add really used functions
Merge pull request #1174 from winzou/fix/item

[Core] Move from preUpdate to onFlush
Rename expression to expr
Merge pull request #1180 from amenophis/expression

Use expressionLanguage into ParametersParser
Fix release ONHOLD sold units

1. Put counting $quantity before change state :) coz we never release ONHOLD.

2. When backorders are off and you try to buy last product-variant (on_hand=1) not available on demand (available_on_demand=0)
inventoryOperator->decrease($units); throws InsufficientStockException
isStockSufficient function doesn't know that ONHOLD units waiting for our order.

We can release ONHOLD units before decrease (like in this PR)
or we should send to decrease fucntion $quantity var.
Merge pull request #1181 from ramol/master

Fix release ONHOLD sold units
Fixed docblock
Merge pull request #1184 from umpirsky/fix/minor-fix-10-03-2014

Fixed docblock