fix closing search dropdown (#1142)

* using a different library for javascript selects, fixing the closing search dropdown
* fix closing dropdown for daterangepicker
* added missing search button for mobile on customer page
* fix meta fields with same names than existing columns

assets/sass/app.scss

@@ -5,7 +5,6 @@
  * file that was distributed with this source code.
  */
 
-@import "~bootstrap-sass/assets/stylesheets/bootstrap/variables";
 @import 'variables';
 @import 'error-page';
 @import 'print';
@@ -24,3 +23,4 @@
 @import 'skins';
 @import 'sweetalert';
 @import 'autocomplete';
+@import 'selectpicker';