Update ParticleType repr

[VeckoTheGecko]

Changes:

• Add ParticleType repr (fixes #1693)
• Patch indentation for pset
• xfail test_mitgcm for "auto" chunk_mode (xref #1762)

Indentation before:

<ParticleSet>
    fieldset   : <FieldSet>
    fields:
        <Field>
            name            : 'U'
            grid            : RectilinearZGrid(lon=array([ 0.00,  0.05,  0.11, ...,  0.89,  0.95,  1.00], dtype=float32), lat=array([ 0.00,  0.05,  0.11, ...,  0.89,  0.95,  1.00], dtype=float32), time=array([ 0.00]), time_origin=0, mesh='flat')
            extrapolate time: True
            time_periodic   : False
            gridindexingtype: 'nemo'
            to_write        : False
        <Field>
            name            : 'V'
            grid            : RectilinearZGrid(lon=array([ 0.00,  0.05,  0.11, ...,  0.89,  0.95,  1.00], dtype=float32), lat=array([ 0.00,  0.05,  0.11, ...,  0.89,  0.95,  1.00], dtype=float32), time=array([ 0.00]), time_origin=0, mesh='flat')
            extrapolate time: True
            time_periodic   : False
            gridindexingtype: 'nemo'
            to_write        : False
        <VectorField>
            name: 'UV'
            U: <parcels.field.Field object at 0x10562acb0>
            V: <parcels.field.Field object at 0x163543a30>
            W: None
    pclass     : <class 'parcels.particle.ScipyParticle'>
    repeatdt   : None
    # particles: 1
    particles  : [
        P[0](lon=0.000000, lat=0.000000, depth=0.000000, time=0.000000)
    ]

After:

<ParticleSet>
    fieldset   :
        <FieldSet>
            fields:
                <Field>
                    name            : 'U'
                    grid            : RectilinearZGrid(lon=array([ 0.00,  0.05,  0.11, ...,  0.89,  0.95,  1.00], dtype=float32), lat=array([ 0.00,  0.05,  0.11, ...,  0.89,  0.95,  1.00], dtype=float32), time=array([ 0.00]), time_origin=0, mesh='flat')
                    extrapolate time: True
                    time_periodic   : False
                    gridindexingtype: 'nemo'
                    to_write        : False
                <Field>
                    name            : 'V'
                    grid            : RectilinearZGrid(lon=array([ 0.00,  0.05,  0.11, ...,  0.89,  0.95,  1.00], dtype=float32), lat=array([ 0.00,  0.05,  0.11, ...,  0.89,  0.95,  1.00], dtype=float32), time=array([ 0.00]), time_origin=0, mesh='flat')
                    extrapolate time: True
                    time_periodic   : False
                    gridindexingtype: 'nemo'
                    to_write        : False
                <VectorField>
                    name: 'UV'
                    U: <parcels.field.Field object at 0x104866cb0>
                    V: <parcels.field.Field object at 0x168d11270>
                    W: None
    pclass     : <class 'parcels.particle.ScipyParticle'>
    repeatdt   : None
    # particles: 1
    particles  : [
        P[0](lon=0.000000, lat=0.000000, depth=0.000000, time=0.000000)
    ]