The domain-mapper calls SwXText::insertTextPortion very extensively
accounting for about half of import time for large, lightly formatted
text documents. The vast majority of the work is consumed managing
char + para properties - so try to batch that, making it 70% faster
for my lightly formatted test. Saves around 25% of load time for me.

Change-Id: I2582adee1bf35b07b90af810cb0d19dadc1d348f