IDE-1229 Define Liferay Language Properties File content type

    Source review for content type, add encoding validation for properties files referenced by portlet.xml and
    liferay-hook.xml.

    The encode of the content type is UTF-8 and the file name should end with
    ".properties".

    It needs to meet 3 conditions
    - in a Liferay project.
    - referenced by either a portlet.xml or liferay-hook.xml
    - in default source folder used by the xml files.
IDE-1229 Source formatting

- externalized isValidFile() method in FileDescriber
- rewrote PropertiesUtil to simply nested code
- moved propertieFile related utils from ProjectUtil to PropertiesUtil