Old number formats had predefined formats from 0..49, locale data could
define additional formats from index 50 on. Internal (fractional)
formats were added to the number formatter, shifting the number of
predefined entries NF_INDEX_TABLE_ENTRIES by two that was also used as
an offset to determine whether a format needed to be added additionally.

As a consequece, formats defined with index values 50 and 51 in locale
data were ignored and not available in the dialog.

Introduced a new enum constant NF_INDEX_TABLE_LOCALE_DATA_DEFAULTS to
use as the old offset value for not having to change all locale data
definitions everytime an internally generated format is added.

Change-Id: I94bdaabf360f7b9c253b1e3f5b73087f0c45fb44