[RFE] Allow multiple groups creation.

Adding an option `groups` to create multiple groups in one operation.
Adding tests (present/absent/external/nonposix) with server and
client context.
Simple example of `groups` option:
```
tasks:
- name: Ensure 2 groups are present
  ipagroup:
    ipaadmin_password: SomeADMINpassword
    groups:
    - name: group1
    - name: group2
```

Signed-off-by: Denis Karpelevich <dkarpele@redhat.com>

tests/group/groups.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+NUM=${1-1000}
+FILE="groups.json"
+
+echo "{" > "$FILE"
+
+echo "  \"group_list\": [" >> "$FILE"
+
+for i in $(seq 1 "$NUM"); do
+    {
+        echo "    {"
+        echo "      \"name\": \"group$i\","
+        echo "      \"description\": \"group description $i\""
+    } >> "$FILE"
+    if [ "$i" -lt "$NUM" ]; then
+       echo "    }," >> "$FILE"
+    else
+       echo "    }" >> "$FILE"
+    fi
+done
+
+echo "  ]" >> "$FILE"
+
+echo "}" >> "$FILE"