Merge pull request #276 from eric-wu/release-1.17

Patch Release 1.17 for DynamoDB RDS synchronizer bugs
Added more tests
Merge branch 'release-1.17' into develop
Merge branch 'wikidao2' into wikidao
Fixed some code review issues and added support for WikiAttachmenthHandles
server side support of PLFM-1710 and PLFM-1707
added dowload wiki attachment file and preview to Synapse java client
Merge pull request #287 from john-hill/wikidao

fixes for PLFM-1710 and PLFM-1707
Removed @Ignores for PLFM-1714, PLFM-1715, PLFM-1716
Merge pull request #288 from john-hill/wikidao

Removed @Ignores for PLFM-1714, PLFM-1715, PLFM-1716