Warehouse base class added
refs #3692
Adding ImageMesh class which builds a mesh based on the size data from
an image file specified by the user.

Remarks:
* This currently works for a single image in 2D, but could be extended
  to work on a stack of images in 3D.
* Can scale the 2D domain to a max dimension of 1, 'scale_to_one=true'.
* User can specify a cells_per_pixel value <= 1 to undersample the image.

Refs #3976.
Merge pull request #3977 from jwpeterson/image_mesh

Adding ImageMesh class to phase_field module
Switching Indicators and Markers to new warehouse

Switch MaterialWarehouse over to Warehouse

Moving constraints over to Warehouse

Covert Dirac Kernel Warehouse over

Coverting VariableWarehouse over

Coverting PostprocessorWarehouse over

Coverting UserObject Warehouse over

Convert AuxKernel Warehouse over

Covert VectorPostprocessors over

Moving splits over

Coverting OutputWarehouse over

Convert Multiapp Warehouse over

Moving DGKernel Warehouse over

Moving Transfer Warehouse over

Moving Action Warehouse over

Moving BC Warehouse over

Move Dampers over
Adding an ImageFunction test which reads into an elemental variable
instead of a nodal variable.

The elemental variable field looks a lot more like the original image
when you have 1 pixel/element.

[original](https://drive.google.com/file/d/0B9BK7pg8se_iU2xFS19aUVVPOGs/edit?usp=sharing)
[elemental](https://drive.google.com/file/d/0B9BK7pg8se_iOUNSUlpfM1RNZUE/edit?usp=sharing)
[nodal](https://drive.google.com/file/d/0B9BK7pg8se_ieEw2S25VUU15S2M/edit?usp=sharing)

Refs #3544.
Merge pull request #3975 from permcody/warehouse_base_squash

Warehouse base squash
Update .gitignore to ignore new output file in phase_field module
Merge pull request #3978 from jwpeterson/image_function_test

Adding an ImageFunction test which reads into an elemental variable