Deprecate unreferenced config.xml.crx and config.xml.wgt

They are current being used ONLY by
- doc/Web_Test_Suite_Developer_Guide.md
- doc/Web_Runtime_Crosswalk_Test_Suite_Developer_Guide.md
- doc/Web_Test_Suite_SIMD_Developer_Guide.md
- doc/Cordova_Test_Suite_Developer_Guide.md
which shall be updated.

Historically, the config.xml.crx was used to package test suites for
Chrome/Chromium extensions as CRX Package Format. It hasn't been used
for a long time.

The config.xml.wgt was used to package test suites for Tizen platforms.
It duplicates the default config.xml
Merge pull request #1440 from zqzhang/config-cleanup

Deprecate unreferenced config.xml.crx and config.xml.wgt