New logo, button and favicon.

1. Logo - for now login page and normal pages use the same logo size.  In future versions, we may include a slightly larger one for the login page.  Didn't want to include this in a minor update, since this is a configurable image name, and hence adding a new logo, may end up with having a mix of two logos.

2. The button is now a scaled version of the logo.  For this reason, it is removed from the footer of the login page, but kept on the others.

3. Added the new favicon.

config_defaults_inc.php

@@ -800,7 +800,7 @@
  * Logo
  * @global string $g_logo_image
  */
-$g_logo_image = 'images/mantis_logo.gif';
+$g_logo_image = 'images/mantis_logo_232x80.png';
 
 /**
  * Logo URL link

core/html_api.php

@@ -491,7 +491,7 @@ function html_top_banner() {
 		if( $t_show_url ) {
 			echo '<a id="logo-link" href="', config_get( 'logo_url' ), '">';
 		}
-		echo '<img id="logo-image" alt="Mantis Bug Tracker" src="' . helper_mantis_url( config_get( 'logo_image' ) ) . '" />';
+		echo '<img id="logo-image" alt="Mantis Bug Tracker" src="' . helper_mantis_url( $t_logo_image ) . '" />';
 		if( $t_show_url ) {
 			echo '</a>';
 		}
@@ -624,12 +624,16 @@ function html_footer( $p_file = null ) {
 
 	echo "<div id=\"footer\">\n";
 	echo "\t<hr />\n";
-	echo "\t<div id=\"powered-by-mantisbt-logo\">\n";
-	$t_mantisbt_logo_url = helper_mantis_url( 'images/mantis_logo_button.gif' );
-	echo "\t\t<a href=\"http://www.mantisbt.org\" title=\"Mantis Bug Tracker: a free and open source web based bug tracking system.\"><img src=\"$t_mantisbt_logo_url\" width=\"88\" height=\"35\" alt=\"Powered by Mantis Bug Tracker: a free and open source web based bug tracking system.\" /></a>\n";
-	echo "\t</div>\n";
 
-	# Show optional user-specificed custom copyright statement
+    # We don't have a button anymore, so for now we will only show the resized version of the logo when not on login page.
+    if ( !is_page_name( 'login_page' ) ) {
+        echo "\t<div id=\"powered-by-mantisbt-logo\">\n";
+    	$t_mantisbt_logo_url = helper_mantis_url( 'images/mantis_logo_232x80.png' );
+    	echo "\t\t<a href=\"http://www.mantisbt.org\" title=\"Mantis Bug Tracker: a free and open source web based bug tracking system.\"><img src=\"$t_mantisbt_logo_url\" width=\"145\" height=\"50\" alt=\"Powered by Mantis Bug Tracker: a free and open source web based bug tracking system.\" /></a>\n";
+    	echo "\t</div>\n";
+    }
+
+    # Show optional user-specificed custom copyright statement
 	$t_copyright_statement = config_get( 'copyright_statement' );
 	if ( $t_copyright_statement ) {
 		echo "\t<address id=\"user-copyright\">$t_copyright_statement</address>\n";