[TIMOB-13646] Validate.py accepts multiple directories

#### How it works
The doc directories to validate can be set in two ways
1. Using -d or -dir followed by a doc path
	* This will take one directory
	* The titanium docs dir will not be included automatically
2. Follow up validate with a list of doc directories separated by spaces
	* Multiple directories can be validated at once
	* The titanium docs dir will be included automatically
To validate multiple directories but not include the titanium docs dir combine the
two methods passing the first directory with -dir and the rest separated by spaces