[webapi][XWALK-1860] Fix unavailable external files

 -Replace unavailable external files with tinyweb links in 12 TCs
 -Remove two TCs which cannot be fixed with tinyweb
 -Fail reason: load image in widget policy does not support

 Impacted tests (approved): New 0, Update 12, Delete 2
 Unit test platform: Tizen IVI
 Unit test result summary: Pass 8, Fail 4, Block 0
Merge pull request #328 from Honry/Honry/Fix-xwalk-1680

[webapi][XWALK-1860] Fix unavailable external files
[webapi][XWALK-1848] Update description for webapi/3dtransforms

Impacted tests(approved): New 0, Update 6, Delete 0
Unit test platform: [Android]
Unit test result summary: Pass 6, Fail 0, Block 0
Merge pull request #329 from minxhuang/hm/xwalk-1848

[webapi][XWALK-1848] Update description for webapi/3dtransforms