Merge pull request #218 from chrox/master

transfer libk2pdfopt to koreader
Initialize FileChooser with root_path, otherwise the command line argument (directory) is ignored
Use `lfs.currentdir()` to get default `root_dir` as an absolute path
Merge pull request #219 from thotypous/master

Initialize FileChooser with root_path, otherwise the command line argument (directory) is ignored
update koreader-base
Merge pull request #221 from thotypous/master

update koreader-base
bugfix: fix screen ghosting after swiping north/south in scroll mode
As swiping north/south will generate several pan gestures which will
set refresh mode to WAVEFORM_MODE_A2, we should explicitly do a full
refresh in order to switch refresh waveform from WAVEFORM_MODE_A2
to WAVEFORM_MODE_GC16 as in OnPanRelease.