Directional block placement support in build mode.

## Suggestion
I have been playing around with using Baritone for building settings, and I'm quite impressed. From my testing, Baritone can build most structures nearly unsupervised. However, unless I'm overlooking some major feature (I've tried a lot of settings, but to no avail) baritone always pauses builds including directional blocks such as stairs. It may place a couple, but not always in the right direction and occasionally it breaks them again entirely. The simplest testing configuration includes just a couple of stairs in different directions placed on a flat floor.

Problematic blocks include torches (mainly against walls), stairs and slabs.

Allowing proper stair placement would allow much more complex/detailed builds, and would put baritone well over other building tools such as schematica. (:

## Settings / implementation.
I fear it wouldn't be too easy to implement, though. The least complex solution I can think of contains at least the following steps:

-Test if the block to be placed is directional.
-Determine the correct relative position to place the block from.
-Place a support block to place the directional block against, unless already present (this step is required, for example upside down stairs have to be placed against a top/side block)
-Navigate to the position to place the block from.
-place the block.

This may cause some problems, however, if this position is not easily reachable. (A good example being an upside down slab above a solid floor.) Baritone may have to break some blocks to get into the required position relative to the block to be placed.
This may be fine, unless the blocks broken are also directional, which would certainly cause a loop. It might be possible to add a setting to add an extra (high) cost for breaking directional blocks.