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
Fix #7927 : Add a warning message if trying to print a composition
as an image fails (Qt's QImage sanity check for memory overflow)
Moved previous commit from core/qgscomposition to apps/qgscomposer
as QGIS server uses qgscomposition.
update GUI translation ja
Merge pull request #670 from tqhien/master

Fix #7927 : Add a warning message if trying to print a composition
Merge pull request #671 from qgis-jp/make_pull_req_from_ja

update GUI translation ja
fix #8131
fix #8099: useful error message on table_info
[spatialite] Implement rewind()
[spatialite] Fix compile error
update Translation GUI ja
Merge pull request #672 from qgis-jp/make_pull_req_from_ja

update Translation GUI ja
[Plugin Manager] If no Python support detected, display an explanation why there is nothing to install. Fixes #8063. PL translation included.
- add missing sip bindings
- port widgets_tree.py to QtXml and update customization.xml (fixes #5752 and  #8054)