Added whitespace handling in cell

[winterheart]

This fixes bug where pyexcel-ods cannot parse multiple whitespaces (<text:s text:c="2"/> and such).

Sorry I don't have test unit for that.

[chfw]

Could you please supply a test fixture and a test case for it?

[winterheart]

Well, I'm not skilled with tests. Here example:

import pyexcel_ods
from collections import OrderedDict

workbook = OrderedDict()
workbook.update({'Sheet 1': [["    Heading spaces"],
                             ["Spaces    between"],
                             ["Trailing spaces    "]]})

pyexcel_ods.save_data("test.ods", workbook)
workbook = pyexcel_ods.get_data("test.ods")
spreadsheet = list(workbook.items())

for row in spreadsheet[0][1]:
    print("'%s'" % row[0])

[chfw]

The test fails. But your proposal shred the light for a better implementation. I would merge the PR and put my changes in too.