Change paste settings and add copyright headers

- There's now a notice reminding people to change the base URL if they
  had a custom base URL and change the paste type (that was something I
  personally had problems with when I was testing, so a reminder was
  helpful for me).

- Broke down some of the long lines on APIPage.cpp to be more readable.

- Added copyright headers where they were missing.

- Changed the paste service display names to the names they are more
  commonly known by.

- Changed the default hastebin base URL to https://hst.sh due to the
  acquisition of https://hastebin.com by Toptal.

launcher/ui/pages/global/APIPage.ui

@@ -61,6 +61,19 @@
             <property name="placeholderText">
              <string/>
             </property>
+            <property name="clearButtonEnabled">
+             <bool>true</bool>
+            </property>
+           </widget>
+          </item>
+          <item>
+           <widget class="QLabel" name="baseURLNote">
+            <property name="text">
+             <string>Note: you probably want to change or clear the Base URL after changing the paste service type.</string>
+            </property>
+            <property name="wordWrap">
+             <bool>true</bool>
+            </property>
            </widget>
           </item>
          </layout>