[ticket/11275] Do not use document.write() for color palette

Replace document.write() for color palette function

PHPBB3-11275
[ticket/11275] Do not use spacer.gif in color picker

PHPBB3-11275
[ticket/11237] Fix PHP error in acp_prune.php

Also making the code a bit more efficient (removing one SQL query)

PHPBB3-11237
[ticket/11236] Correct HTML

PHPBB3-11236
[ticket/11236] Do not require group selection in prune users

PHPBB3-11236
[ticket/11236] Change PRUNE_USERS_GROUP_EXPLAIN language

PHPBB3-11236
Merge remote-tracking branch 'remotes/cyberalien/ticket/11275' into develop
Merge PR #1370 branch 'EXreaction/ticket/11237' into develop

# By Nathaniel Guse
# Via Nathaniel Guse
* EXreaction/ticket/11237:
  [ticket/11237] Fix PHP error in acp_prune.php
Merge PR #1371 branch 'EXreaction/ticket/11236' into develop

# By Nathaniel Guse
# Via Nathaniel Guse
* EXreaction/ticket/11236:
  [ticket/11236] Change PRUNE_USERS_GROUP_EXPLAIN language
  [ticket/11236] Do not require group selection in prune users
  [ticket/11236] Correct HTML