MDL-61852 lib: move popper.js to core

Popper is used in tool_usertours. Bootstrap 4 stable depends on popper too. Moving to /lib so both can use a single popper.js lib

admin/tool/usertours/amd/readme_moodle.txt

@@ -8,10 +8,3 @@ Flexitour Instructions
 4. Change the "popper" inclusion to "./popper"
 5. Update thirdpartylibs.xml
 6. Run `grunt amd`
-
-Popper.js Instructions
-----------------------
-1. Clone https://github.com/FezVrasta/popper.js into an unrelated directory
-2. Copy /build/popper.js to amd/src/popper.js
-3. Update thirdpartylibs.xml
-4. Run `grunt amd`

admin/tool/usertours/amd/src/tour.js

@@ -2,7 +2,7 @@
 (function (root, factory) {
   if (typeof define === 'function' && define.amd) {
     // AMD. Register as an anonymous module unless amdModuleId is set
-    define(["jquery","./popper"], function (a0,b1) {
+    define(["jquery","core/popper"], function (a0,b1) {
       return (root['Tour'] = factory(a0,b1));
     });
   } else if (typeof module === 'object' && module.exports) {

lib/amd/readme_moodle.txt

@@ -0,0 +1,6 @@
+Popper.js Instructions
+----------------------
+1. Clone https://github.com/FezVrasta/popper.js into an unrelated directory
+2. Copy /build/popper.js to amd/src/popper.js
+3. Update thirdpartylibs.xml
+4. Run `grunt amd --force`

lib/thirdpartylibs.xml

@@ -303,4 +303,11 @@
     <license>GPL</license>
     <licenseversion>2.0+</licenseversion>
   </library>
+  <library>
+    <location>amd/src/popper.js</location>
+    <name>Popper.js</name>
+    <license>MIT</license>
+    <version>v1.12.9</version>
+    <licenseversion></licenseversion>
+  </library>
 </libraries>