Adjust for the splitting of number format properties in chart.

Since 1d38cb365543924f9c50014e6b2227e77de1d0c9, "number format" and
"link number format to source" properties are 2 separate properties.  Adjust
OOXML import code for that split.

Also, always set axis' number format via NumberFormat property even when it's
a percent format.  The axis object doesn't keep a non-percent and percent
number formats separately.

Change-Id: I8667b6f1a78d88cc37d059518919ad1b37f154e1
bnc#881025: Mark axis a percent axis only when all data series are percent.

Change-Id: I302cc1e5b164b2ce9999087293b034ec930951af
bnc#881025: Write test for this.

Change-Id: Ifb1f83bbe5f9bb9ecb7fca26f883d1331052f10d