Gallery2: update content start/end once getUpdateinfo

When delete last picture in album , the album has changed,
but this time current index and content start/end is still
old value.

To aviod this situation, will update content start and content end
once after getUpdateinfo and then can get correct current index and
item path.

CRs-Fixed: 624471

Change-Id: I8eb92e685f321df2d11481f440f7d9d33cf7b820
Gallery2: Fix the string can't  be translated in Gallery2.

The string is defined in FilterDrawRepresentation.java with English.

Extract this string into source.xml file and get it by getString().

CR-fixed: 623893

Change-Id: Ied7afc964555cfd752af306742be69eba4a41349