New endpoint - ie_mixed_content to set IE's Mixed Content.
Missed file for checkin for ie_mixed_content.
Add Registry Key's to JsonCodec. Fix IEMixedContent to use Strings
instead of booleans.
Merge branch 'mixed_content' of https://github.com/smccarthy/Selenium-Grid-Extras into smccarthy-mixed_content

Conflicts:
	SeleniumGridExtras/src/main/java/com/groupon/seleniumgridextras/utilities/json/JsonCodec.java
Merge branch 'smccarthy-mixed_content'
Grouping Windows specific JSON info into Windows class
Updating changelog with new features