Initial commit for Conditional Equations

a) Add a hook for equation altering
b) Create a new module for Conditional Equations feature

includes/sp-core-functions.php

@@ -1291,6 +1291,9 @@ if ( !function_exists( 'sp_get_eos_safe_slug' ) ) {
 
 if ( !function_exists( 'sp_solve' ) ) {
 	function sp_solve( $equation, $vars, $precision = 0, $default = 0 ) {
+		
+		// Add a hook to alter $equation
+		$equation = apply_filters( 'sportspress_equation_alter', $equation, $vars );
 
 		if ( $equation == null )
 			return $default;