Fieldnames in multiple exemple

[Raizencorp]

Describe the bug
When a pcd file get for exemple :
FIELDS x y z _ intensity ring _
where _ are juste empty field who have a count number as below:
COUNT 1 1 1 4 1 1 10

To Reproduce
run Pyntcloud.from_file('path/to/file.pcd)

Expected behavior
error warning, "ValueError: field '__0000' occurs more than once"

Desktop (please complete the following information):

• OS: ubuntu 18.04
• Version master branch

Fix
`
def build_dtype(metadata):
""" build numpy structured array dtype from pcl metadata.
note that fields with count > 1 are 'flattened' by creating multiple
single-count fields.
TODO: allow 'proper' multi-count fields.
"""
fieldnames = []
typenames = []
count = 0
for f, c, t, s in zip(metadata['fields'],
metadata['count'],
metadata['type'],
metadata['size']):
np_type = pcd_type_to_numpy_type[(t, s)]
if c == 1:
fieldnames.append(f)
typenames.append(np_type)
else:
fieldnames.extend(['%s_%04d' % (f, i + count) for i in range(c)])
count += c
typenames.extend([np_type] * c)

# This modify the fieldnames automatically generated who create an error

dtype = np.dtype(list(zip(fieldnames, typenames)))
return dtype

`
add a count to prevent repetition on dataframe