Icon: name for icons

Name for icons with 2 words separated by a minus sign can be created now from cameCase string or underscored strings.
Eg.: Icon::th_large() or Icon::thLarge()
Icon: name for icons - tests updated
Icon: __normaliseIconString

Replace underscores with minus sign and transform from camelCaseString to camel-case-string code moved to __normaliseIconString function.
Merge pull request #222 from crlcu/master

Icons: name for icons with 2 words