Merge pull request #669 from qgis-jp/make_pull_req_from_ja

update GUI translation ja
[ftools,gdaltools] Errors in Merge Shapefiles and Split vector layer
* Fix #8120
* Fix #8119
[Plugin Manager] Fixes #8122: Scroll bar in new plugin manager doesn't work properly
[Plugin Manager] Follow up commit:b16cc46
Fix WFS layer items in browser
fix crash in plugin installer
[dbmanager] Fix python error
identation update and fix clang 3.3 warnings
Use a new ogr layer per iterator
Remove driver
Set filter on iterator:
Close active iterators
Merge branch 'iterator'

Semi fix #7472.
Semi fix #7862
vector providers: allow multiple iterators - testing required
context_help/function_help:
- remove en_US postfix
- remove translated files (translation were moved to ts files earlier)
- remove unused jQuery (python help doesn't use it anymore)
- change expression label in QgsQueryBuilder and add context help (partly fixes
  #8129)
german translation update
update GUI translation ja