Html2Pdf.php: Add error codes and a hint on wkhtml fails.

SendMail.php: in error message show commandline.
test.html: remove

Patch for sendEmail (see https://unix.stackexchange.com/a/68952).

qfq-letter.css.less: redefined h1, letter-receiver

Store.php, AbstractBuildForm.php, QuickFormQuery.php, Save.php: change signature of appendToStore() to be eqal to setStore().
Unittests for appendToStore.php

Manual.rst:

Download.php, Html2Pdf.php, Link.php, SendMail.php: Add TOKEN_PAGE as a valid source for download. This should be the same as TOKEN_URL_PARAM.

sendMail refactored - AutoCron.php,Report.php,SendMail.php: SENDMAIL_IDX_* replaced by SENDMAIL_TOKEN_*

SendMail.php: renamed file and class from 'sendmail' to 'sendMail'. Remove obsolete function buildHeader().
AutoCron.php: Update use of class sendMail().
FormAction.php: rename function sendmail(0 to doSendMail().
Report.php: remove unnecessary code. Move sendmailConvertToken() to class sendMail / parseStringToArray().

Sendmail.php: log attachments in MailLog too.

Sendmail.php: Remove the optin '-q'  (quiet) from 'sendEmail' to see problems with broken parameter. Fix problem with missing '-a' for first attachment. Escape all Shell arguments before calling 'sendEmail'. Recode attachmentsBuild().

Bug - PHP Warning: Declaration of qfq\BuildFormTable::head() should be compatible with qfq\AbstractBuildForm::head($mode = qfq\FORM_LOAD)  - fixed

Manual.rst: sendMailToken 'f' changed from  'f' to 'F'.
Download.php, Linnk.php: TOKEN_FILE_DEPRECATED
Sendmail.php: broken, in the middle of work

BuildFormBootstrap.php: make buildPillNavigation dynamicUpdate aware.
QuickFormQuery.php: Fix problem with missing HTML_ID in FE.

Bug #5031 / Missing details in DbException: New definition of SYSTEM_SHOW_DEBUG_INFO: even after config.qfq.ini is parsed and SIP Infos has been read - if there is no BE User logged in, the value stays on 'auto' (earlier it has been replaced to 'no'). Staying on 'auto' keeps the information that replacing is still open and not replaced means 'no'-BE User logged in.