fixed project_url field and added instruction for tuning

templates/login/theme.properties.j2

@@ -1,3 +1,28 @@
+#parent= the parent then defaults to d4science
+#titleTag= the page title is mandatory
+#favicon= absolute url to favicon defaults to https://services.d4science.org/favicon.ico
+#contentBgImg= relative path to bg image defaults to img/color-triangles.png
+#contentStyle= define custom styles. Note: use this for overriding BG image when pointing to external resource such as background: url("https://url-of-background-img"i no-repeat center center fixed); background-size: cover;
+
+#logoHeaderStyle= custom style for logoHeader defaults to display: flex; justify-content: space-between; width: 100%;
+
+#logoSrc= url for logo image is mandatory
+#logoAlt= alt text for logo gCubeDev Gateway
+#logoStyle= custom style for logo defautls to height: 60px;
+#infrastructureLogo= yes (default) if "powered for d4science has to be included". no otherwise
+#infrastructureLogoStyle= custom style for infrastructureLogo defaults to height: 40px;
+#footerStyle= custom style for footer defaults to: display: flex; flex-direction: column; width: 100%; padding-top: 10px;
+#linkTerms= absolute url to terms of use 
+#linkCookies= absolute link to cookie policy
+#linkPrivacy= absolute link to privacy policiy defaults to: https://www.iubenda.com/privacy-policy/441050
+#linkProject= absolute link to project home site
+#descrProject= description of project
+
+#ECLogo= include EC logo defaults to no
+#ECLogoStyle= custom style for EC logo defaults to max-width: 35px;
+#ECLogoAlt= alt text for EC logo defaults to EU H2020 programme
+#footerRow= custom HTML text for footer content
+
 parent={{ parent_theme }}
 
 {% if styles is defined and styles %}