We need to tell libxml2 parser to decode entities.

Else we would get raw entity values such as '&#38;' in lieu of '&'.

Change-Id: Ib700705fd9b68980306883aa9652579e1686040d
(cherry picked from commit 285cd8301c725cceead97d645f22fd92ba644492)
Add test to make sure sheet names with '&' get imported correctly.

Change-Id: Iea7bb77cdbd5f3ba3b658c373b7d4156b2ca6337
(cherry picked from commit 3b47c8fda324af275aac9e6d237b6da6c8e5ca00)