Add integer attribute of particle

[ChunYen-Chen]

This PR allows the user to use integer attributes of particles and solves part of #79.

Changes

• PAR_TYPE is now a built-in integer attribute.
• Loading PAR_IC is updated.
• Wiki pages about particles are updated.
• Rename PAR_NATT_USER to PAR_NATT_FLT_USER.

New

• A new script create_PAR_IC.cpp to generate new PAR_IC files.
• A new compilation option INT8_PAR (--long_par in configure.py) to control the precision of the integer attributes.
• A new compilation option PAR_NATT_INT_USER (--par_attribute_int in configure.py).

Note

• yt module does not recognize the integer attribute type correctly.
• gamer_compare_data is not supported yet.
• libyt is also not supported yet.

[ChunYen-Chen]

@hyschive Thanks for the review. I have addressed the comment. Please take another review.

[hyschive]

@ChunYen-Chen I encountered the following error messages when using gamer_compare_data with the old data format, for both HDF5 and C-binary formats:

CompareParticleData ...
********************************************************************************
ERROR : particle integer arrays have not been allocated yet !!
        Rank <0>, file <Main.cpp>, line <439>, function <CompareParticleData>
********************************************************************************

I suspect the issue arises because Aux_AllocateArray2D() returns NULL when the array size is zero.

[hyschive]

@ChunYen-Chen I've added some final minor comments, including a few bug fixes. Please also resolve the conflicts.