Move codes generating html file from xml files to SettingsLib (1/2)

LicenseHtmlGeneratorFromXml, LicenseHtmlLoader and indirecly AsyncLoader
shoud be commonly used by Settings and TvSettings.

So this CL will move them to SettingsLib.

Test: building succeeded and tested on sailfish.
  make ROBOTEST_FILTER=SettingsLicenseActivityTest RunSettingsRoboTests

Change-Id: I12e9169b1d3d313a6c5da0d575a6526327268381