bug fix in readerfont

After set font in ReaderFont:onReadSettings, we have to send UpdatePos
event in order to set m_is_rendered(member of LVDocView) to true.

Otherwise position inside document will be reset to 0 on first view
render, this makes the first page of document is always displayed on
document open.

So far, I don't know why this call will alter the value of m_is_rendered.
It just works...
3 new cre methods from @kai771

renamed from kai's commit:

* setViewMode
* setHeaderInfo
* setHeaderFont
use predefined variable instead of magic number for view_mode
add page status to readerrolling for better page view_mode support

* now when rendering in page view mode, we only keep track of page
number instead of pos inside document. Because using pos inside
document for page view mode is really a bad idea and will lead to
many unsovlabe bugs...
update k2pdfopt to version 1.6.3
add libk2pdfopt as a prerequisite lib for kpdfview object
Demo version of koptreader config dialog.
add config options
first usable koptreader for new UI
make pdfreader and djvureader the defaults
larger option text in paperwhite
save/restore koptconfig to setting files
Merge pull request #678 from houqp/new_ui_sync

update from master branch
Merge pull request #674 from houqp/new_ui_houqp

bug fix in readerfont & minor code adjustment & page status in readerrolling
bug fix in menu widget, call close_callback on after select
add toc menu for touch UI
bug fix: signal ViewRecalculate event after panning

This make sure ReaderPaging get correct visible_area when
turnning to previous page.
adapt ReaderPanning to new touch event system
bug fix: set toc menu height and width
add ignore attribute to CenterContainer widget