PATLAB-7 add page-template tests

	 * Retrieves (handlebars) page template

	 * 

	 * if no page template is set yet, returns the default 

	 * gui doc-page template

	 * gui doc-page templateto be used in a series of similar 

	 * pages with iterating data

	 * 

	 * it retrieves a compiled Handlebars template and

     * returns the rendred page content when invoked

    /**

     * Sets and compiles (handlebars) page by page filename

     * for a *Patternlibrary* page template to be used in a 

     * series of similar pages with iterating data

     * 

     * if `page` is a '.md' or '.markdown' file, it is also 

     * passed through the markdown renderer

     * var rendered = P.pagetemplate(pagevars);

     * ```

     * 

     * if the parameter does not correspond to a readable file

     * the parameter's string value is assigned as page template 

     * 

     * look-up order:

     * - project's doc pages dir (pages src dir + basepath)

     * - project's `gui` pages dir

     * - module's `gui` pages dir

     * - file path

     * 

     * @param {string} page - the file basename of the page-file

     * @var {function} pagetemplate - a precompiled (handlebars) template

    		var pagefile = path.join(this.options.root, this.options.basepath, page);

    		var guipage  = resolvePath(path.join(this.options.gui.pages, this.options.basepath, page));

        	try {

    		if ( !fs.existsSync(pagefile) ) {

        		if ( fs.existsSync(guipage) ) {

        			// file from gui pages

    			// file from pages

        		pageSource = fs.readFileSync(pagefile).toString();

    		}

        	} catch (e) {

        		this.log.warn('Error loading Patternlibrary pagefile "'+pagefile+'"');

        		throw new Error(e.message);

        	}

    	}

    	// strip yml data in the beginning

    	pageSource = fm(pageSource).body;

    	try {

		// finally compile Markdown content, if we have a markdown file here...

		if (markdown) {

    		// and renders some special characters useless for to be interpreted by 

    		// Handlebars, like `{{> ...`, so we wrap it with Handlebars and let its

    		// MarkdownIt helper there do it...

        		pageSource = '{{#md}}'+pageSource+'{{/md}}'; 

    		pageSource = '{{#markdown}}'+pageSource+'{{/markdown}}'; 

		}

    	} catch (e) {

    		this.log.warn('Error rendering Markdown content');

    		throw new Error(e.message);

    	}

    	this._pageTemplate = this.handlebars.compile(pageSource, {noEscape: true});

    }