Add cache support

[MekDrop]

Implements #162.

Now admin_menu, editors_list and waiting block uses caching lib for cache own data. At current moment only file caching is enabled.

[fiammybe]

Looks like I have an issue with this one on the admin.php page :

Message: Integer or \DateTime object expected.
Code: 0
File: C:\xampp56\htdocs\prepa6\vendor\apix\cache\src\PsrCache\Item.php
Line: 191
Trace:
#0 C:\xampp56\htdocs\prepa6\vendor\apix\cache\src\PsrCache\Item.php(71): Apix\Cache\PsrCache\Item->expiresAt(1519888082)
#1 C:\xampp56\htdocs\prepa6\vendor\apix\cache\src\PsrCache\TaggablePool.php(52): Apix\Cache\PsrCache\Item->__construct('waiting_touch', NULL, 1519888082, false)
#2 C:\xampp56\htdocs\prepa6\modules\system\blocks\system_waiting.php(24): Apix\Cache\PsrCache\TaggablePool->getItem('waiting_touch')
#3 C:\xampp56\htdocs\prepa6\libraries\icms\view\block\Object.php(262): b_system_waiting_show(Array)
#4 C:\xampp56\htdocs\prepa6\libraries\icms\view\PageBuilder.php(286): icms_view_block_Object->buildBlock()
#5 C:\xampp56\htdocs\prepa6\libraries\icms\view\PageBuilder.php(128): icms_view_PageBuilder->buildBlock(Object(icms_view_block_Object), Object(icms_view_Tpl))
#6 C:\xampp56\htdocs\prepa6\libraries\icms\view\PageBuilder.php(69): icms_view_PageBuilder->retrieveBlocks()
#7 C:\xampp56\htdocs\prepa6\libraries\icms\view\theme\Object.php(242): icms_view_PageBuilder->xoInit()
#8 C:\xampp56\htdocs\prepa6\libraries\icms\view\theme\Factory.php(109): icms_view_theme_Object->xoInit()
#9 C:\xampp56\htdocs\prepa6\libraries\icms\response\HTML.php(433): icms_view_theme_Factory->createInstance(Array)
#10 C:\xampp56\htdocs\prepa6\libraries\icms\response\HTML.php(35): icms_response_HTML->setThemeFromConfig(Array)
#11 C:\xampp56\htdocs\prepa6\include\cp_functions.php(66): icms_response_HTML->__construct(Array)
#12 C:\xampp56\htdocs\prepa6\admin.php(82): icms_cp_header()
#13 {main}

[MekDrop]

I think I have fixed this one too.

[MekDrop]

Test, merge #203 first. Than I'll be able to fix this one.