Merge pull request #273 from chrox/master

add DHINTCOUNT in defaults.lua
Merge pull request #277 from chrox/master

update koreader-base
Merge pull request #283 from chrox/master

update mupdf and k2pdfopt to the latest version
Merge pull request #284 from chrox/master

update koreader-base
Merge pull request #286 from chrox/master

update mupdf.patch in koreader-base
update translation
update readmes
Merge pull request #287 from houqp/houqp-master

readme udpate
estimate cache size of koptcontext
This should fix #285.